AIO or air cooler?

An AIO is not better for most gaming CPUs: a dual-tower air cooler such as the £26.90 Thermalright Peerless Assassin 120 SE suits a 120 W Ryzen 7 9800X3D, with no pump to fail. A 360 mm AIO is the better buy for 250 W chips such as the Intel Core Ultra 7 270K Plus, for the 170 W Ryzen 9 9950X3D and for cases with less than 155 mm of cooler height.

The temperature gap is real at high power. Tom's Hardware measured the ARCTIC Liquid Freezer III Pro nearly 15 °C cooler than the air coolers in its chart with a Ryzen 9 9950X3D held at 150 W and a 290 W graphics load. The chips themselves are ranked in Best CPU for gaming UK 2026.

Which gaming CPUs need an AIO?

Only chips rated well above the Ryzen 7 X3D's 120 W need an AIO: the Core Ultra 7 265K and 270K Plus, which Intel rates at 250 W of maximum turbo power, and the 170 W Ryzen 9 9950X3D. Tom's Hardware chose 150 W as the worst gaming power it had seen reported for the 9950X3D, and notes that stock settings limit the chip to 200 W.

Ryzen 7 X3D chips sit below that line. TechSpot measured 128 W of average EPS power for the Ryzen 7 9800X3D and 162 W for the 9850X3D. Tom's Hardware's best CPU coolers guide, updated 22 June 2026, says the Peerless Assassin cooled a Core i9-12900K drawing over 200 W better than the rival air coolers, names it the best air cooler for most people, and advises a bigger cooler only for the highest-end CPUs under sustained all-core work, or for the quietest possible PC. The ARCTIC costs £40.59 more than the Peerless Assassin, about 2.5 times the price, and that money buys temperature headroom.

Will an air cooler or a 360 mm AIO fit your case?

The Thermalright Peerless Assassin 120 SE, 155 mm tall, fits six of the eight cases below; the 168 mm Noctua NH-D15 G2 fits four. A 360 mm radiator fits seven, provided it is thin enough. Each limit is the case maker's published figure.

Radiator thickness is the check most buyers miss. ARCTIC says the Liquid Freezer III Pro 360 needs at least 63 mm, because its radiator is 38 mm thick before the 25 mm fans, and Tom's Hardware warns it will not fit every case. NZXT allows a 30 mm radiator, about 60 mm with fans, on the NZXT H6 Flow's roof, its only 360 mm mount. A 27 mm radiator fits there: MSI lists the MAG CORELIQUID A13 360 at 394 x 119.6 x 27 mm and Gigabyte the AORUS WATERFORCE II 360 at 394 x 119 x 27 mm. The Fractal Design North shows the other trade: 145 mm rules out both tower coolers, and its front 360 mm radiator cuts graphics card room to 300 mm. Case fans matter as much as the cooler; see How many case fans do I need?

Does an AIO last as long as an air cooler?

Usually not: an air cooler's only wearing parts are its fans, which a standard fan replaces, while an AIO's pump sits inside the sealed loop, so a pump failure usually means a new cooler. A replacement ARCTIC P12 Pro 120 mm fan costs £6.25 on Amazon UK at the time of writing (October 2026).

MSI publishes a life rating on its datasheet: 25,000 hours for the pump in the MAG CORELIQUID A13 360 and 40,000 hours at 40 °C for its fans. That is about 8.6 years at eight hours a day, or 2.9 years in a PC left on around the clock. Warranties tell a similar story, with 5 to 6 years on the big-brand AIOs below. The last column divides the Amazon UK price by the warranty years.

The ARCTIC is the cheapest AIO per year of cover at £11.25, and only the Peerless Assassin undercuts it overall. The Corsair and NZXT ranges are compared in Best Corsair products UK 2026 and Best NZXT products UK 2026.

Which cooler should you buy?

The ARCTIC Liquid Freezer III Pro 360 is the AIO to buy, at £67.49 on Amazon UK at the time of writing (October 2026), for a Core Ultra 7 270K Plus, a Ryzen 9 9950X3D or any build that wants the lowest temperatures. Tom's Hardware names it the best 360 mm AIO and ARCTIC backs it for 6 years. For a Ryzen 7 9800X3D, the £26.90 Peerless Assassin 120 SE is enough.

Tom's Hardware gave the Liquid Freezer III Pro five stars after it tamed a Ryzen 9 9950X3D with Precision Boost Overdrive enabled, a load under which even the Hyte THICC Q60 throttled. The trade-off is noise: Tom's Hardware measured 52.6 dBA at full fan speed, so a gentler fan curve in the BIOS is worth setting. The small VRM fan on the pump block cools the motherboard's power stages, and Intel builds use ARCTIC's included contact frame.

Verdict

An AIO is better only when the CPU or the case demands it. For a Ryzen 7 9800X3D, the Thermalright Peerless Assassin 120 SE at £26.90 is enough and has no pump to wear out; for a 250 W Core Ultra 7 270K Plus or a Ryzen 9 9950X3D, the ARCTIC Liquid Freezer III Pro 360 at £67.49 is the one to buy, case depth permitting. The CPUs to pair with either are ranked in Best CPU for gaming UK 2026.