OnePlus 15T vs Vivo X300 Ultra

OnePlus 15T

Snapdragon 8 Elite Gen 5 paired with 12-16GB LPDDR5X Ultra Pro RAM delivers flagship synthetic scores — Notebookcheck recorded Geekbench multi-core 10,976 and 3DMark Wild Life Unlimited 29,901, on par with the larger Xiaomi 17 and Honor Magic8 Pro Air. The problem is sustained: in the 3DMark Wild Life stress test the GPU drops over 50% and the back of the phone hits 50 °C, which both Notebookcheck and SuperSaf flag as a deal-breaker for long gaming sessions.

• Geekbench 6 multi-core hits 10,976 — flagship-tier and within 1% of the average 8 Elite Gen 5 result, so there is no compromise on the chipset versus larger phones.
• 3DMark Wild Life Unlimited hits 29,901 — 5% above the 8 Elite Gen 5 average and ahead of the Xiaomi 17 with the same chip.
• In the 3DMark stress tests the OnePlus 15T shows a sharp drop in performance of over 50%, which significantly lowers our rating.
• Wildlife Extreme stress test scores swung from 6,990 best loop to 3,743 worst loop in a single run — the chart is 'quite a bit of a bumpy ride' and performance mode did nothing to stabilize it.
• Surface temperatures hit 48.3 °C on the back during stress testing and continued climbing to 50 °C near the camera bump — about 45 °C internal — which seems to be the phone's thermal limit.
• Genshin Impact averaged 60.3 fps over 30 minutes at just 3.2 W power draw, with the phone staying cool to the touch — and Peacekeeper Elite pushed 164.5 fps thanks to native 165 Hz support.
• r/Android's reviewer thread flags the same thermal issue directly: 'Gets kinda hot, over 50 degrees in the corner. This is with its very heavy throttling.'

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.

OnePlus 15T

This is the section the OnePlus 15T was built to win. The 7,500 mAh silicon-carbon 'Glacier' cell is the largest ever fitted to a true compact phone — 50% bigger than the iPhone 17's pack in a similar footprint. Notebookcheck measured roughly 1.5 days of real-world endurance at 150 cd/m². Wired charging tops out at 100 W, wireless at 50 W. The only friction points are the missing built-in magnets for MagSafe-style alignment and the still-USB-2.0 port.

• OnePlus relies on a silicon-carbon-based battery with a large capacity of 7,500 mAh for its mini flagship — in our practical battery test at 150 cd/m² brightness, the 15T achieved an excellent battery life of nearly 1.5 days.
• 9to5Google's preview confirms the 7,500 mAh cell carries the same 'Glacier' moniker as the OnePlus 15's battery, so the silicon-carbon structure is here too — 200 mAh more than the larger sibling.
• Even though the phone keeps the same compact size, it now packs a massive 7,500 mAh battery — to put that into perspective, the iPhone 17 Pro Max only has around 5,000 mAh, and this is a 6.32-inch phone.
• Battery life is wild for a phone this size and is actually a hair bigger than the one in the OnePlus 15, which has a noticeably larger footprint.
• 100W SuperVOOC wired charging and 50W wireless mean even the huge cell refills fast — getting through two full days on a single charge feels totally realistic.
• There is no native magnetic Qi alignment — wireless charging works, but accessories require a separate magnetic case for MagSafe-style snap-on functionality.
• r/Android's reaction to the battery is unambiguous — 'Incredible battery life makes the compact smartphone competition pale in comparison' is the actual review-thread headline.

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.