Vivo X300 Ultra vs Xiaomi 15 Ultra

Vivo X300 Ultra

A 6.82-inch 144Hz LTPO AMOLED, now flat rather than quad-curved. Lab measurements put real brightness near 1,900 nits in auto and ~3,300 nits on a small window — among the best panels on any phone — and reviewers single out content consumption and clarity as standouts.

• We measured a maximum of over 1,900 nits in auto-brightness mode and over 3,300 nits when lighting up a smaller portion of the screen.
• Consuming content, scrolling the web, pixel-peeping and zooming in on text — it doesn't get any clearer, or with the 144Hz any smoother, than the display on the X300 Ultra.
• It delivers an excellent max brightness of around 1,935 nits with a 75% white pattern and a peak of 3,328 nits with a 10% pattern.
• Vivo has gone with a flat display this time, a clear shift from the quad-curved style of the X200 Ultra.
• It's a 6.82-inch AMOLED with a claimed 4,500-nit HDR peak that can reach that figure in a one-person window watching HDR content; PWM sits around 3.5% at max brightness, better for flicker-sensitive users.
• An absolutely stunning display with terrific, bass-heavy stereo speakers to match.

Xiaomi 15 Ultra

A 6.73-inch 2K AMOLED with curved edges, 120Hz, a 3,200-nit peak and 1,920Hz PWM dimming. Reviewers call it gorgeous and one of the brightest screens around, with the lone caveat that real-world auto-brightness measured lower than the headline number.

• The 6.73-inch display is gorgeous, super sharp and crazy bright — fantastic indoors and out, second only to the Galaxy S25 Ultra in direct sunlight thanks to Samsung's anti-glare tech.
• On paper it has the brightest screen at 3,200 nits (vs 2,600 on the Samsung, 2,000 on the iPhone) and supports 1,920Hz PWM dimming so it flickers much less than its rivals.
• Lab testing clocked ~3,175 nits at 20% APL — basically stare-at-the-sun-and-still-see-your-screen territory.
• The maximum achievable auto-brightness is only around 1,150 nits, which is rather disappointing for this level of phone, though still usable under sunlight.
• It has 3,200 nits peak brightness across a 25% area rather than the usual 1% window — a genuinely usable peak.

Vivo X300 Ultra

Snapdragon 8 Elite Gen 5 plus Vivo's custom imaging silicon delivers flagship benchmark numbers and strong gaming, but the camera-heavy hardware runs hot — sustained stress tests show roughly 60–65% stability and the camera app warms it up fast.

• At the heart is Qualcomm's current flagship Snapdragon 8 Elite Gen 5, supplemented by Vivo's custom VS1 and V3-Plus imaging chips.
• It boots in 16 seconds (vs 21s for the S26 Ultra and 19s for the iPhone 17 Pro Max) and posts an AnTuTu score over 3,800,000, stronger than Samsung.
• In a prolonged stress test it throttled CPU performance to about 60% of peak — in line with other high-powered flagships — and 3DMark stability landed around 63–66%.
• It gets a bit hot after 30–40 minutes of gaming, but with no throttling even past an hour and never uncomfortable to hold; boost mode at max graphics gives around 4 hours of Wuthering Waves on a full charge.
• Native 120fps gaming with smooth/very-high graphics in many titles, with temperature barely crossing 35°C and power draw around 4W in battle-royale modes.
• Under sustained camera/imaging load the front reached ~46.8°C and the back ~45.2°C, and around 47°C the refresh rate drops slightly though not all the way to 60Hz.

Xiaomi 15 Ultra

Snapdragon 8 Elite with up to 16GB RAM and UFS 4.1 — flagship-grade and still excellent a year on. Real-world gaming holds ~57–60fps with acceptable power draw, though heavy synthetic stress tests show meaningful throttling.

• Runs Qualcomm's Snapdragon 8 Elite with up to 16GB RAM and 1TB UFS 4.1; 10 months on it's still an extremely well-balanced phone that feels like a true flagship.
• In ~50 minutes of gaming it held a stable ~57–60fps with 4–8W draw — acceptable for the 8 Elite — where some rivals throttle hard and drop to 30fps after 30 minutes.
• After 30 minutes of real gaming with apps closing/reopening the CPU sat around 47°C with no overheating — heat only appears in synthetic 3DMark/throttle benchmarks, not realistic use.
• In a 3DMark stability run it scored ~70–76% stability (lowest loop ~4,335–4,542), holding 20–43fps.
• Under a punishing 60-minute 100-thread CPU throttle test it dropped roughly 40–50% in sustained performance, recovering only slightly better than the S25 Ultra.

Vivo X300 Ultra

Vivo grew the silicon-carbon cell 10% to 6,600mAh while keeping the body the same size. Real-world endurance is strong — ~16h active-use score, ~7h heavy screen-on, 13–14 hour days with charge to spare — and 100W wired refills it in under an hour, with 40W wireless.

• Vivo increased the battery by 10% to 6,600mAh despite the phone being practically the same size on paper.
• In our battery test it earned an active-use score of almost 16 hours; 100W charging took it 0–66% in 30 minutes and a full charge in 46 minutes, plus 40W wireless. A charger is in the box except in Europe.
• On the China version I'm finishing entire 13–14 hour days with 25–30% left; the global version keeps the 6,600mAh cell so battery life should comfortably last 12–13 hours of heavy use.
• Getting nearly 7 hours of screen-on time with very heavy usage from the 6,600mAh silicon-carbon unit, with 100W wired and 40W wireless charging support.
• After a 4-hour heavy-usage simulation the phone still had ~45% battery left, which is solid by today's standards, and 100W wired charging takes about 45 minutes to full.
• In a head-to-head charge race against the Oppo Find X9 Ultra (80W), the Vivo on 100W finished first at 50 minutes 20 seconds to the Oppo's 52:39.

Xiaomi 15 Ultra

The global model's ~5,410mAh cell (vs 6,000mAh in China) is the phone's weakest area — many reviewers end the day under 30%, with a notable idle drain — though 90W wired charging fully refills it in roughly an hour and Chinese-variant users report much better longevity.

• The global variant has a smaller 5,410mAh cell vs the 6,000mAh China variant, and most days the phone is around or under 30% by the end of the day — it could have done with a bigger battery.
• With always-on display, 120Hz and intensive camera use it consistently achieved over 15 hours of usage on a single charge in real-world testing.
• On the global/Indian 5,410mAh battery, the in-box 90W charger refills it roughly: 18% in 5 min, 67% in 30 min, 90% in 45 min, and a full charge in about an hour.
• On the Chinese 6,000mAh variant with a power-efficient chip, the battery was still at 78% after not charging for three nights.
• There's a real idle-drain issue — 20 minutes of light morning use can drop 5–6%, and it persists even with extra-dim settings enabled.