Air and liquid coolers both move heat from the processor to the air in your room. The difference is where that happens and what it costs, and the popular framing of liquid as simply better is wrong.
In short
- A good air cooler matches most 240 mm liquid coolers on performance.
- Liquid coolers move heat away from the socket area, which helps in tight cases.
- Air coolers have one moving part per fan. Pumps fail, and they fail over years.
- Choose on clearance, noise and case layout rather than on category.
How each works
An air cooler conducts heat into a metal base, through heat pipes, into a stack of fins, and a fan blows that heat into the case air. It is entirely passive apart from the fan.
A liquid cooler moves heat into a coolant, pumps it to a radiator usually mounted at the front or top of the case, and fans there move it into the case air. The pump is an additional moving part and an additional failure point.
Neither removes heat from the case. Both put it into the air inside, which case fans then exhaust.
Performance, honestly
A good dual-tower air cooler is comparable with a 240 mm liquid cooler and within a few degrees of many 360 mm units. The gap opens up at the highest sustained power levels, where large radiators have more surface area to work with.
For most processors, either is more than adequate, and the choice comes down to the practical considerations below rather than to a temperature difference you would never notice.
Reasons to choose air
Fewer failure points. A fan that fails is audible and cheap to replace. A pump that fails may not be obvious until the processor starts reducing its clock speed.
No pump noise, which some people find more intrusive than fan noise because it is constant and higher pitched.
Lower cost for equivalent performance, and a service life limited only by the fan bearings.
Reasons to choose liquid
Clearance. A large air cooler can conflict with tall memory modules, the top of the case, or the first expansion slot. A radiator moves that bulk elsewhere.
It removes a large mass from directly above the socket, which improves airflow to the memory and voltage regulators in compact builds.
Sustained high-power processors benefit from the larger radiator surface area.
Service life
An air cooler has one wearing part per fan, and a fan is cheap and obvious when it fails. The heatsink itself lasts indefinitely. A decade-old air cooler with a new fan performs as it did when new.
A closed-loop liquid cooler has a pump, and pumps wear out. Coolant also permeates slowly through the tubing over years, and the loop cannot be topped up. Manufacturers typically warrant them for five or six years, which is a reasonable indication of expected life.
A failing pump is not always obvious. The symptom is rising temperatures and the processor reducing its clock speed, which is easy to attribute to dust or thermal paste. Worth checking pump speed in firmware monitoring if an older liquid cooler starts underperforming.
Where to mount a radiator
Front mounting draws cool room air through the radiator, which gives the best processor temperatures, but that air is then warmer by the time it reaches the graphics card.
Top mounting exhausts through the radiator using air already warmed by the system, so the processor runs slightly warmer while everything else runs slightly cooler.
For most builds top mounting is the better balance, particularly with a hot graphics card. Front mounting suits a build where processor temperature is the priority.
One practical point regardless of position: if the pump sits at the highest point in the loop, air collects in it and causes noise. Mounting the radiator so its top edge is above the pump avoids this, which is another argument for top mounting.
Whichever you choose, check clearance. For air, the cooler height against what the case allows, and memory module height against the cooler. For liquid, the radiator size against the case mounting positions, and radiator thickness as well as length, since thicker radiators can foul the top of the motherboard.