Vivo X300 Ultra vs Xiaomi 15

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

A small but flagship-grade flat AMOLED with class-leading peak brightness. Outdoor visibility is a recurring highlight.

• An independent test clocked the display at 3,175 nits at 20% APL — bright enough to comfortably read in direct sun.
• The phone offers 3,200 nits of peak brightness; a year on, the screen still feels flagship-level for YouTube, Netflix and gaming.
• There is a dedicated sunlight mode you toggle in settings that boosts the panel up to 3,200 nits.
• Whether watching video or gaming, after a year the display still feels flagship level.

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

Snapdragon 8 Elite makes it one of the fastest small phones available, and it holds sustained performance better than larger rivals — but it still runs warm under prolonged synthetic and 4K-video loads.

• It runs the Snapdragon 8 Elite — pretty much the fastest chipset available on any smartphone at launch.
• In a stress test against the Galaxy S25 and Oppo Find X8, the Xiaomi 15 won on stability (~72%) versus the S25's 67% and the Find X8's 58.6%, and also had the upper hand in Geekbench.
• Despite being a much smaller phone tested in hotter conditions, it sustained better performance and smoothness than an iQOO 13 in a 10-loop benchmark; an external cooler lifted the lowest-loop score 14%.
• The chipset swap to the Snapdragon 8 Elite is welcome, but just like last year the Xiaomi 15 still struggles to keep it cool under prolonged loads.
• A year on the flagship chipset is still very powerful and the phone's performance remains solid in 2026.

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

A ~5,240mAh cell that beats a Galaxy S25 in head-to-head rundowns and recharges very fast over both wire and wireless — though a HyperOS idle drain divides reviewers.

• The Xiaomi 15 packs a larger ~5,240mAh battery versus a Galaxy S25's ~4,000mAh while only being 27g heavier, and ended a head-to-head rundown at 30% vs the S25's 13%.
• It charges in around 45 minutes with the 90W adapter in the box, and the reviewer had zero issues with battery life in normal mixed use.
• From a fully dead battery a measured charge test reached 66% in 45 minutes, 91% at 1h05m and a full 100% in about 1h15m.
• It also supports 50W wireless charging — faster than typical flagship wired speeds — though there are no Qi magnets built in, so you need a 50W-compatible mat for top speed.
• Xiaomi says battery can run roughly 25% longer than the Xiaomi 14.