Samsung Galaxy S25 Ultra 512GB VS Xiaomi 15 Ultra

Both the Samsung Galaxy S25 Ultra and the Xiaomi 15 Ultra share the same core protection credentials — an IP68 rating and full waterproofing — so neither has an edge on durability. In day-to-day handling, however, the differences in physical form factor are more meaningful than they might first appear. The S25 Ultra is notably slimmer at 8.2 mm versus the Xiaomi's 9.4 mm, a 1.2 mm gap that is genuinely perceptible in-pocket and in-hand. Combined with a lower total volume (103.6 cm³ vs 114.2 cm³), the Samsung occupies meaningfully less space despite being slightly taller and wider.

The weight gap reinforces this story: the S25 Ultra comes in at 218 g while the Xiaomi 15 Ultra tips the scale at 229 g. An 11-gram difference may sound marginal on paper, but on a device you hold for hours daily it translates to a lighter feel over extended use — particularly during one-handed operation or prolonged reading sessions. The Xiaomi is also slightly narrower at 75.3 mm vs 77.6 mm, which helps offset some of that weight disadvantage in terms of grip, but it cannot fully compensate for the bulk added by the greater thickness.

On design, the Samsung Galaxy S25 Ultra holds a clear advantage. It is lighter, thinner, and occupies less overall volume, making it the more pocketable and ergonomically comfortable of the two. Neither phone offers a rugged build or a foldable form factor, so those dimensions are a wash. For users who prioritize a sleeker, less imposing flagship, the S25 Ultra is the stronger choice based purely on these specs.

Both screens are OLED/AMOLED panels with 1440p resolution and a 120Hz refresh rate, so the baseline viewing experience is premium on either device. The real separation begins with brightness and contrast: the Xiaomi 15 Ultra outputs a significantly higher 3200 nits of typical brightness against the S25 Ultra's 2600 nits, making it noticeably more readable under direct sunlight. The contrast gap is even more striking — 8,000,000:1 on the Xiaomi versus 3,000,000:1 on the Samsung — which translates to deeper perceived blacks and more punch in HDR content.

The Xiaomi also edges ahead on pixel density (522 ppi vs 498 ppi) despite its smaller 6.73″ screen compared to the Samsung's 6.9″, meaning text and fine detail appear marginally crisper. Its 300Hz touch sampling rate versus 240Hz on the S25 Ultra is a spec that matters primarily to mobile gamers, where faster touch polling reduces input latency. Adding to its display credentials, the Xiaomi supports Dolby Vision — a format the S25 Ultra lacks entirely — giving it a wider range of premium streaming HDR content rendered as the creator intended. The Samsung counters with branded damage-resistant glass, which the Xiaomi does not have, offering better real-world scratch and drop protection for the screen.

On display quality alone, the Xiaomi 15 Ultra holds the stronger hand: higher brightness, a dramatically better contrast ratio, finer pixel density, faster touch response, and Dolby Vision support all point in its favor. The S25 Ultra's advantage of branded protective glass is a meaningful practical consideration, but it is a durability trade-off rather than a display quality one. Users who prioritize visual performance will find the Xiaomi's panel the more capable of the two.

At the silicon level, these two phones are built on identical foundations: both run the Qualcomm Snapdragon 8 Elite on a 3nm process with the Adreno 830 GPU, identical memory bandwidth, and the same thermal envelope. The meaningful differences emerge in how each manufacturer has tuned that shared hardware. The Samsung Galaxy S25 Ultra runs its prime CPU cores at a higher clock of 4.47 GHz versus 4.32 GHz on the Xiaomi 15 Ultra, and its GPU boost clock is set higher at 1200 MHz compared to 1100 MHz. That GPU advantage is reflected in the 3DMark Steel Nomad score, where the S25 Ultra leads with 2318 against the Xiaomi's 2152.

Yet the broader benchmark picture tells a different story. The Xiaomi 15 Ultra posts a substantially higher AnTuTu score of 2,746,580 versus the S25 Ultra's 2,207,809 — a gap of roughly 24% — and also leads in both Geekbench 6 single-core (3234 vs 3057) and multi-core (10,059 vs 9,846) results. This suggests the Xiaomi's overall system-level performance tuning and its larger 16GB of RAM (versus 12GB on the Samsung) contribute to snappier real-world responsiveness, particularly when multitasking or running memory-intensive workloads. More RAM directly means more apps stay active in the background without being reloaded.

The verdict here is split by use case. For sustained GPU-intensive gaming, the S25 Ultra's higher graphics clock gives it a narrow edge. For general system performance and heavy multitasking, the Xiaomi's benchmark lead and extra RAM make it the stronger performer. On balance, the Xiaomi 15 Ultra holds a broader performance advantage across the data provided, even though both devices share the same flagship chip.

Both phones field a quad-camera rear system anchored by a 200MP primary sensor with OIS, 4K/30fps 8K capability, and identical top-level shooting features like RAW capture, phase-detection autofocus, and laser autofocus. The divergence lies in the telephoto configuration. Samsung equips the S25 Ultra with a 5x optical zoom lens, edging out the Xiaomi 15 Ultra's 4.3x, which is a tangible reach advantage for distant subjects. The Xiaomi counters by replacing the Samsung's 10MP fourth lens with a 50MP shooter, delivering far more resolution headroom on that extra focal length. Notably, the Xiaomi's periscope lens features a large 1.6 µm pixel size, compared to just 1.12 µm on the S25 Ultra's corresponding telephoto — larger pixels capture more light per cell, which matters especially in low-light zoom scenarios.

The selfie camera gap is hard to ignore: the Xiaomi offers a 32MP front sensor with a wider f/2.0 aperture versus the S25 Ultra's 12MP at f/2.2. More megapixels mean better-cropped portraits and more detail in good light, while the wider aperture helps in dim conditions. For video enthusiasts, the Xiaomi also supports Dolby Vision recording — a format the S25 Ultra cannot capture — which is significant for anyone editing or sharing content within the Apple/Dolby ecosystem. The S25 Ultra's BSI sensor on its main camera is a structural advantage for dynamic range in challenging light, but the Xiaomi does not carry that designation.

The DxOMark score provides a useful summary signal: the Xiaomi 15 Ultra scores 153 against the S25 Ultra's 146, consistent with its advantages in front camera resolution, telephoto pixel size, and video format support. The S25 Ultra's edge in optical zoom reach keeps it competitive for telephoto purists, but on the overall camera package, the Xiaomi 15 Ultra holds a clear advantage based on the provided data.

Running identical Android 15 bases, these two phones share the vast majority of their software feature sets — privacy controls, dynamic theming, split-screen multitasking, PiP, offline voice recognition, widgets, and more are present on both. For most users, day-to-day software experience will feel broadly comparable. The differences, while few, are practical rather than superficial.

The Samsung Galaxy S25 Ultra has two exclusive capabilities in this data set. First, Wi-Fi password sharing — a small but genuinely convenient feature for anyone who regularly hosts guests or sets up new devices. Second, and more significantly, the ability to be used as a PC via a desktop mode, which allows the phone to power a monitor, keyboard, and mouse setup as a full computing environment. The Xiaomi 15 Ultra lacks this feature entirely. In contrast, the Xiaomi does not support cross-site tracking blocking in its browser, whereas the S25 Ultra does — a modest but real privacy advantage for everyday web browsing without additional configuration.

The operating system category is largely a tie in scope, but the S25 Ultra's desktop PC mode is the single most impactful differentiator here, offering a genuine productivity use case that the Xiaomi cannot match. For users who value software versatility and the occasional need to work from their phone on a larger screen, the Samsung Galaxy S25 Ultra holds a clear, if narrow, edge in this group.

The battery category presents a genuine paradox. The Xiaomi 15 Ultra carries a substantially larger 6000 mAh cell versus the S25 Ultra's 5000 mAh — a 20% capacity advantage — yet the provided battery life figures tell the opposite story: the Samsung Galaxy S25 Ultra lasts 31 hours compared to just 19 hours on the Xiaomi. Based strictly on this data, the S25 Ultra is significantly more efficient at translating raw capacity into usable screen time, which is what actually matters day to day. A 12-hour gap in rated battery life is not marginal — it is the difference between a phone that comfortably lasts a full day and one that may need a midday top-up for heavy users.

Where the Xiaomi fights back decisively is in charging. Its 90W wired charging speed is double the S25 Ultra's 45W, meaning it will recover from empty to full in roughly half the time. The wireless charging gap is even more dramatic: 80W on the Xiaomi versus just 15W on the Samsung, making wireless charging a genuinely fast option on the Xiaomi rather than an overnight convenience. Reverse wireless charging follows the same pattern — 10W versus 4.5W — useful for topping up earbuds or a smartwatch. The Xiaomi also ships with a charger included, while Samsung does not, which is a practical cost consideration out of the box.

This group ultimately comes down to a clear trade-off: endurance versus speed. For users who prefer to charge less frequently and prioritize all-day longevity, the Samsung Galaxy S25 Ultra holds the stronger hand based on the rated battery life figures. For those who charge often and want that process to be as fast as possible, the Xiaomi's charging ecosystem is in a different league. On the more universally valued metric of how long the phone lasts between charges, the S25 Ultra has the edge.

Wired audio is off the table for both phones — neither carries a 3.5mm headphone jack — so the wireless codec stack becomes the critical battleground. Both support aptX, aptX HD, and LDAC, covering the most widely used high-resolution Bluetooth audio formats and ensuring compatibility with the majority of premium wireless headphones on the market. The Xiaomi 15 Ultra, however, goes two steps further with aptX Adaptive and aptX Lossless support, which the S25 Ultra lacks entirely. aptX Adaptive dynamically adjusts bitrate for lower latency and more stable connections, while aptX Lossless — as the name implies — enables CD-quality audio transmission over Bluetooth when paired with compatible headphones. For audiophiles invested in the Qualcomm wireless ecosystem, this is a meaningful gap.

The microphone count also favors the Xiaomi, which fields 4 microphones versus 3 on the S25 Ultra. Additional microphones generally improve noise cancellation, spatial audio capture, and voice pickup accuracy during calls and video recording — particularly in windy or noisy environments. It is a quiet but practical advantage for anyone who records frequently or relies on call clarity.

With a richer Bluetooth codec stack and an extra microphone, the Xiaomi 15 Ultra holds a clear edge in audio capability based on the provided specs. The S25 Ultra covers the essentials well, but for users who prioritize wireless audio fidelity — especially with next-generation aptX hardware — the Xiaomi is the stronger choice in this category.

The core connectivity stack is essentially identical — both phones offer Wi-Fi 7, 5G, USB 3.2 Type-C, NFC, and matching peak download and upload speeds. The Xiaomi 15 Ultra pulls ahead with Bluetooth 6.0 versus the S25 Ultra's 5.4, a newer standard that brings improved connection stability, lower latency, and better coexistence with other wireless signals — relevant for anyone pairing frequently with multiple devices. The Xiaomi also adds an infrared sensor, turning the phone into a universal remote for TVs and appliances, and critically includes emergency SOS via satellite — a safety feature that lets the phone send distress signals in areas with no cellular coverage whatsoever. The S25 Ultra has neither of these.

Samsung fights back with two meaningful exclusives. The inclusion of a stylus is a productivity differentiator that transforms the phone for note-taking, sketching, and precise on-screen input in a way no software feature can replicate. On the SIM side, the S25 Ultra supports 2 physical SIMs plus 2 eSIMs, offering considerably more flexibility for travelers or dual-line users compared to the Xiaomi's 2 physical SIMs only with no eSIM support — a notable omission in 2025. The S25 Ultra also supports ANT+, a protocol used by fitness equipment and sports sensors, though this is a niche advantage relevant only to specific users.

This group is genuinely competitive, with each phone holding advantages the other cannot match. The Xiaomi's satellite SOS and newer Bluetooth version address safety and future-proofing, while the Samsung's stylus and dual eSIM support offer a richer productivity and travel experience. On balance, the two phones split this category — the right winner depends entirely on whether a user values safety and wireless refinement (Xiaomi) or input versatility and SIM flexibility (Samsung).

The Miscellaneous spec group offers no differentiation between these two phones whatsoever. Both have a video light, neither features sapphire glass, a curved display, or an e-paper secondary screen — every data point is an exact match. This is a complete tie by the provided data, and no advantage can be assigned to either device.