Choosing among these three flagship Android phones means weighing a current, high-capacity OnePlus against two renewed Samsung models with different strengths. The OnePlus 15 is my lead pick for its 16GB of RAM, 512GB of storage, large battery, and unlocked carrier support. The Galaxy S21 Ultra makes more sense for buyers who want a large screen, long-range zoom, and S Pen support, while the Galaxy S23 FE offers a smaller display and familiar Samsung features in an AT&T configuration.
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Those strengths come with distinct compromises: OnePlus is physically large, while the Samsung phones are renewed and have less storage. The S23 FE also lists AT&T as its carrier, so compatibility deserves attention before choosing it. I rank these by how completely they deliver a flagship experience today, then by the specific buyer needs each serves. All three can be compelling, but their age, condition, network fit, and hardware differ enough that the best choice depends on which tradeoff you can accept.
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Key Takeaways
- The unlocked OnePlus 15 ranks first for buyers who want 16GB RAM, 512GB storage, a 7,300mAh battery, and broad carrier compatibility in one current model.
- The renewed Galaxy S21 Ultra is the camera reach pick, pairing a 108MP main camera with up to 100x zoom and S Pen support, though it has only 128GB storage.
- The renewed Galaxy S23 FE has the most compact display here at 6.4 inches, but its AT&T configuration warrants a carrier compatibility check.
- Both Samsung options are renewed, so their condition and battery history are meaningful considerations absent from the OnePlus product details.
- For heavy gaming, media, or large photo libraries, OnePlus’s 165Hz display and 512GB capacity offer more headroom than either Samsung‘s 128GB configuration.
| OnePlus 15 Unlocked Dual-SIM Smartphone, 16GB RAM, 512GB Storage, Ultra Violet |  | Best Overall | Operating system: Android 16 | Processor: Snapdragon 8 Elite Gen 5 | Memory and storage: 16GB RAM; 512GB storage | VIEW LATEST PRICE | See Our Full Breakdown |
| Samsung Galaxy S21 Ultra 5G, US Version, 128GB, Phantom Black – Unlocked (Renewed) |  | Best for Zoom and S Pen Support | Display: 6.8-inch AMOLED, 120Hz | Main camera: 108MP | Zoom: Up to 100x | VIEW LATEST PRICE | See Our Full Breakdown |
| Samsung Galaxy S23 FE 5G, 128GB, Graphite, AT&T (Renewed) |  | Best for a Smaller Samsung Display | Display: 6.4-inch OLED, 1080 × 2340, 120Hz | Processor: Snapdragon, listed at 3GHz | Memory and storage: 8GB RAM; 128GB storage | VIEW LATEST PRICE | See Our Full Breakdown |
| flagship Android smartphone | Display | Processor | Memory and storage | Rear cameras |
|---|---|---|---|---|
| OnePlus 15 Unlocked Dual-SIM S | 6.78-inch AMOLED, 2772 × 1272, 165Hz | Snapdragon 8 Elite Gen 5 | 16GB RAM; 512GB storage | Three 50MP cameras |
| Samsung Galaxy S21 Ultra 5G | 6.8-inch AMOLED, 120Hz | — | — | — |
| Samsung Galaxy S23 FE 5G | 6.4-inch OLED, 1080 × 2340, 120Hz | Snapdragon, listed at 3GHz | 8GB RAM; 128GB storage | Triple camera system with HDR and slow-motion modes |
More Details on Our Top Picks
OnePlus 15 Unlocked Dual-SIM Smartphone, 16GB RAM, 512GB Storage, Ultra Violet
The OnePlus 15 is my top choice because its listed hardware covers more flagship priorities at once than either Samsung here. Its Snapdragon 8 Elite Gen 5, 16GB of RAM, and 512GB of storage leave more room for demanding apps, multitasking, and a large offline library than the S21 Ultra or S23 FE, both listed with 128GB storage. The 6.78-inch AMOLED panel also has a 165Hz refresh rate, a step above the Samsung phones’ 120Hz screens. That matters most to buyers who value responsive scrolling and gaming; ordinary tasks do not require such a high refresh rate.
Battery capacity is another distinguishing point. At 7,300mAh, the OnePlus has the largest stated battery of these three, although capacity alone cannot establish real-world endurance. Its triple 50MP rear cameras and 32MP front camera make it a versatile specification set, but megapixel counts do not guarantee better photos than Samsung’s cameras. The S21 Ultra, in particular, specifies up to 100x zoom, a specialized reach that OnePlus’s listing does not claim.
Being unlocked with dual SIM gives this model a cleaner fit for people who switch networks or need two lines than the AT&T S23 FE. It also lists IP66, IP68, IP69, and IP19K resistance ratings and a one-year manufacturer warranty. The tradeoff is its large 6.78-inch body, which is less appealing if pocket comfort or one-handed use is the priority. Buyers choosing it for the camera should seek sample photos and detailed independent comparisons, since the product summary does not establish image processing quality, telephoto range, or low-light results.
Pros:- 16GB RAM and 512GB storage provide substantially more listed capacity than either Samsung model.
- The 6.78-inch AMOLED screen supports a 165Hz refresh rate for especially fluid motion.
- A 7,300mAh battery is the largest stated capacity in this comparison.
- Unlocked dual-SIM support and listed IP resistance ratings suit flexible daily use.
Cons:- Its large display may feel unwieldy to people who favor compact phones.
- The listing does not specify zoom range or provide detailed evidence of camera performance.
Best for: Buyers who want an unlocked, current-generation Android phone with generous memory and storage, a high-refresh display, and a high-capacity battery.
Not ideal for: People who prefer a compact phone, prioritize a documented long-zoom camera, or want independently verified camera and battery performance before buying.
- Operating system:Android 16
- Processor:Snapdragon 8 Elite Gen 5
- Memory and storage:16GB RAM; 512GB storage
- Display:6.78-inch AMOLED, 2772 × 1272, 165Hz
- Rear cameras:Three 50MP cameras
- Front camera:32MP
- Battery:7,300mAh
- Network and SIM:Unlocked 5G; dual Nano-SIM
- Resistance and warranty:IP66, IP68, IP69, IP19K; one-year manufacturer warranty
Our verdict“I rank the OnePlus 15 first for its broadest combination of current hardware, storage, battery capacity, and unlocked flexibility.”
Samsung Galaxy S21 Ultra 5G, US Version, 128GB, Phantom Black – Unlocked (Renewed)
The Galaxy S21 Ultra is the specialist in this group. Its 6.8-inch AMOLED screen and 120Hz refresh rate keep it in flagship territory for display size and smoothness, while the listed 108MP main camera and up-to-100x zoom set it apart from both the S23 FE and the OnePlus 15. That zoom range appeals to people who want to frame distant subjects from a fixed position, though a maximum zoom figure does not promise equally useful detail at every magnification.
Its other unusual advantage is S Pen support. For annotation, handwriting, or precise input, that can make the S21 Ultra more versatile than the S23 FE and OnePlus as described here. It is also listed as a US version and unlocked, which avoids the S23 FE’s explicit AT&T restriction, though buyers should still check band and carrier compatibility where they live.
The compromises are substantial enough to keep it in second place. This is a renewed device with no battery health details in the listing, and it offers 128GB of storage—less than a quarter of the OnePlus 15’s capacity. Its large 6.8-inch size is also not a compact alternative to the 6.4-inch S23 FE. I would choose it for the camera reach and stylus support, not simply because its original tier was premium. Buyers should confirm what is included and what condition standard applies to the specific renewed unit.
Pros:- The 108MP main camera and listed up-to-100x zoom offer the most explicit long-range camera capability here.
- S Pen support enables note-taking and precise input absent from the other two listings.
- Its 6.8-inch 120Hz AMOLED display provides a large canvas for video and multitasking.
- The US version is listed as unlocked with 5G connectivity.
Cons:- Renewed condition means the individual unit’s wear and battery health should be checked.
- 128GB storage is limited compared with the OnePlus 15’s 512GB.
- Its 6.8-inch size will not suit buyers seeking a compact phone.
Best for: Buyers who want an unlocked renewed Samsung phone with long-range zoom, a very large display, and S Pen support.
Not ideal for: People who need substantial built-in storage, want a new device, or prioritize verified battery condition and a smaller handset.
- Display:6.8-inch AMOLED, 120Hz
- Main camera:108MP
- Zoom:Up to 100x
- Storage:128GB
- Connectivity:5G
- Carrier status:Unlocked; US version
- Special feature:S Pen support
- Condition:Renewed
Our verdict“I recommend the S21 Ultra for zoom and S Pen use, while its renewed status and limited storage make it less versatile overall than the OnePlus 15.”
Samsung Galaxy S23 FE 5G, 128GB, Graphite, AT&T (Renewed)
The Galaxy S23 FE is the most manageable screen size among these options: its 6.4-inch OLED is notably smaller than the S21 Ultra’s 6.8 inches and the OnePlus 15’s 6.78 inches. It still lists a 120Hz refresh rate, so buyers do not have to trade smooth scrolling for a less expansive screen. Its triple rear camera system includes HDR and slow-motion modes, a useful mix for everyday photography and video, though the listing does not give sensor resolution or zoom range for a direct camera comparison.
Its 8GB RAM and 128GB storage are adequate for a more moderate workload, but they leave less capacity for app-heavy use and large media libraries than the OnePlus 15’s 16GB and 512GB. The S21 Ultra also has 128GB storage, yet makes a stronger case for camera reach and S Pen support. That leaves the S23 FE’s appeal in its smaller footprint and straightforward Samsung feature set, rather than maximum performance or photographic range.
The biggest practical caveat is the AT&T configuration. Buyers should confirm compatibility and activation requirements before purchase, particularly if they use another carrier. The renewed condition adds another unknown: the listing does not specify battery health or the cosmetic state of the individual unit. I would place this third for a broad flagship roundup, but it can still make sense for someone who specifically wants a smaller Samsung phone and has verified network fit and renewal terms.
Pros:- A 6.4-inch OLED screen is the smallest and most hand-friendly display in this lineup.
- The 120Hz refresh rate supports fluid scrolling and interface motion.
- Its triple rear camera system lists HDR and slow-motion modes for varied everyday capture.
- 8GB RAM, 128GB storage, and 5G cover a capable baseline smartphone setup.
Cons:- The AT&T carrier configuration may restrict compatibility for some buyers.
- Renewed condition is listed without battery health or unit-specific wear details.
- 128GB storage and 8GB RAM provide less headroom than the OnePlus 15.
Best for: Samsung users who want a 6.4-inch screen, 120Hz refresh rate, and a familiar feature set, and who can use the AT&T configuration.
Not ideal for: Buyers needing carrier flexibility, large storage, verified battery condition, or advanced zoom and stylus features.
- Display:6.4-inch OLED, 1080 × 2340, 120Hz
- Processor:Snapdragon, listed at 3GHz
- Memory and storage:8GB RAM; 128GB storage
- Rear cameras:Triple camera system with HDR and slow-motion modes
- Video capture:1080p at 60fps
- Connectivity:5G and Wi-Fi
- Carrier:AT&T configuration
- Condition:Renewed
Our verdict“The S23 FE is my pick for a smaller Samsung display, provided the AT&T configuration and renewed condition fit the buyer.”
How We Picked
I compared these three listings against the promise of a flagship Android phone: strong display hardware, capable cameras, modern connectivity, useful performance headroom, and a build of features that can serve as a primary device. I gave the most weight to the combination of listed specifications and day-to-day flexibility, rather than treating a single headline feature as proof of overall superiority.
That method favors the OnePlus 15 because its listed Snapdragon 8 Elite Gen 5 processor, 16GB RAM, 512GB storage, 165Hz AMOLED panel, and 7,300mAh battery form the broadest all-around package in this group. The S21 Ultra ranks next for its premium-class screen, 108MP camera and up-to-100x zoom, plus S Pen support; its renewed condition and 128GB storage temper that appeal. The S23 FE places third as a more modest option with a 6.4-inch 120Hz OLED and three rear cameras, but its carrier-specific listing and renewed condition reduce its fit as a universal flagship recommendation.
I also treated missing information as a limit, not as an invitation to guess. The OnePlus listing includes a one-year manufacturer warranty, while the Samsung listings identify renewed condition without giving battery health details. I cannot infer the exact condition of a particular renewed unit, camera performance in every situation, or compatibility with every carrier from these summaries. A buyer should confirm the seller’s condition terms and check network bands and activation status, especially for the AT&T S23 FE.
| flagship Android smartphone | Processor | Rear cameras |
|---|---|---|
| OnePlus 15 Unlocked Dual-SIM S | Snapdragon 8 Elite Gen 5 | Three 50MP cameras |
| Samsung Galaxy S21 Ultra 5G | — | — |
| Samsung Galaxy S23 FE 5G | Snapdragon, listed at 3GHz | Triple camera system with HDR and slow-motion modes |
Factors to Consider When Choosing Best Flagship Android Smartphones
Flagship phones differ most when the headline specifications meet your own habits. I would make the choice here by starting with network compatibility and condition, then comparing screen size, storage, and camera needs. That approach matters especially because the listings combine a newer unlocked OnePlus with two renewed Samsung models.
Match the phone to your carrier
Network fit can outweigh a strong feature list. The OnePlus 15 is listed as unlocked, and the S21 Ultra is also listed as unlocked and a US version. The S23 FE is specifically an AT&T configuration; anyone using another carrier should verify compatibility and activation requirements before ordering. Unlocked status is helpful, but it does not by itself confirm support for every carrier band or every regional network feature. Check the exact model and network requirements for the service you plan to use.
Choose a screen size you can live with
The S23 FE’s 6.4-inch display is the practical choice for buyers who want a less expansive phone. The S21 Ultra grows to 6.8 inches, while the OnePlus 15 is 6.78 inches, giving both more room for video, documents, and split-screen use. All three list high refresh rates: 120Hz for the Samsung models and 165Hz for OnePlus. That difference may matter to people sensitive to motion smoothness, but screen size and comfortable handling are likely to affect daily use more often.
Prioritize the camera feature you actually need
These summaries describe different camera strengths. The S21 Ultra names its 108MP main camera and up-to-100x zoom, so it is the clearest fit for buyers seeking distant-subject framing. The OnePlus lists three 50MP rear cameras, but no zoom range, while the S23 FE specifies a triple-camera setup with HDR and slow-motion modes without naming sensor resolutions. Camera counts and megapixels alone cannot tell me which phone produces the most consistent photos. If image quality is your deciding factor, compare sample images for the kinds of scenes you shoot.
Estimate your storage needs
Storage is a straightforward point of separation: the OnePlus 15 lists 512GB, while both Samsungs list 128GB. That extra capacity suits large photo and video libraries, downloaded media, or a long stretch between cleanup sessions. A buyer who mainly streams media and keeps a modest number of apps may be comfortable with 128GB, but the listings do not state whether storage can be expanded. Treat the available built-in capacity as the working limit unless the exact model’s expansion options are confirmed.
Factor renewed condition into the comparison
The Galaxy S21 Ultra and S23 FE are both marked renewed. That can make an older premium design accessible, but the supplied details do not establish a specific unit’s battery health, cosmetic grade, or included accessories. Review the seller’s condition definition and return terms, and ask about battery coverage if that information is available. The OnePlus listing states a one-year manufacturer warranty, which gives it a clearer warranty detail in this comparison; buyers should still verify the terms and regional coverage.
Balance battery capacity against evidence
The OnePlus 15 lists a 7,300mAh battery, which is substantially specified and suggests a priority on capacity. The Samsung summaries do not provide battery capacities or expected runtime, and the renewed status makes unit condition particularly relevant. Capacity figures do not translate directly into time between charges because screen use, signal conditions, and software workloads all matter. Buyers who rely on all-day endurance should look for independent runtime measurements and, for a renewed Samsung, details about the battery in the actual unit.
Frequently Asked Questions
Which of these phones is the best overall flagship choice?
I rank the OnePlus 15 first because its listing combines a current-generation processor, 16GB RAM, 512GB storage, a 165Hz AMOLED display, a 7,300mAh battery, and unlocked dual-SIM support. The S21 Ultra has a more explicit long-zoom feature and S Pen support, while the S23 FE has a smaller screen, but neither matches the OnePlus’s listed capacity and breadth. Buyers who care most about stylus input or a smaller Samsung device may reasonably prefer one of those alternatives.
Which model is best for zoom photography?
The Galaxy S21 Ultra is the clear choice from the information provided, since its listing names a 108MP main camera and up to 100x zoom. The OnePlus 15 lists three 50MP rear cameras without a zoom range, and the S23 FE description does not specify one. Maximum zoom is not the same as consistently sharp results at every distance, so I would check independent camera samples if far-away subjects are central to your decision.
Is the Galaxy S23 FE compatible with carriers beyond AT&T?
The product is described as an AT&T configuration, so I would not assume it will work fully on another carrier. Compatibility depends on the exact device variant, network bands, activation status, and the carrier’s policies. Before buying, confirm those details with the seller and your carrier. The OnePlus 15 and S21 Ultra listings both identify their phones as unlocked, which makes them more flexible starting points, though exact network support still merits a check.
Should I buy a renewed Samsung phone over the OnePlus 15?
A renewed Samsung can be the better fit when its specific advantage matters most: choose the S21 Ultra for listed zoom and S Pen support, or the S23 FE for a smaller 6.4-inch Samsung screen. The OnePlus is the stronger broad recommendation for buyers who want more listed storage, memory, battery capacity, and an unlocked configuration. The Samsung listings do not state battery health or unit-specific condition, so review seller terms and available coverage before deciding.
Which phone is easiest to carry?
The Galaxy S23 FE has the smallest stated display at 6.4 inches, compared with 6.78 inches on the OnePlus 15 and 6.8 inches on the S21 Ultra. Display diagonal does not reveal a phone’s full dimensions or weight, so it is only a useful first clue rather than a complete measure of comfort. Still, buyers who want less screen area to manage are more likely to find the S23 FE appealing than either larger-screen alternative.
Conclusion
For a single all-around recommendation, I would choose the OnePlus 15: it has the broadest listed hardware package, the most storage, and unlocked dual-SIM flexibility. Pick the Galaxy S21 Ultra if long-range zoom and S Pen support matter more than newer listed hardware or storage headroom, and you are comfortable evaluating a renewed unit. Choose the Galaxy S23 FE if a smaller Samsung display is your priority and you have confirmed the AT&T configuration works for you. The right flagship is the one whose strengths match your routine, with its condition and network fit checked before purchase.
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