The cooling should be better, especially with higher wattage chips (either out of the box, or overclocked). The AIOs have gotten a lot better with faster pumps.

Noise should also be lower again assuming you'd be actually cooling enough power with an air cooler that'd require higher fan RPMs. Pump noise differs by model, with quite a lot of them being silent

try with 800W xeon/threadripper

The guys who built my 9995wx threadripper pro system believed that AIO was basically necessary for the chip. The radiator part of it covers almost the entire top of my case, pushing air through.

The coolers get so heavy that they don't make good contact if your motherboard is not horizontal. For mainstream CPUs that's why a cheap closed loop cooler is better.

Depends on the CPU - X3D's really don't need it, the X's can if you want to uncap the power limits.

I put a 420mm AIO on a 7950X3D (because I was originally getting a 7950X but the X3D went on sale) - the fans barely come on most of the time and the absolute hottest I've ever got it was 77C during the soak in test (stress-ng on 32 cores for a few hours).

If I was building another on say the 9800X3D I'd go back to air - the AIO's only have a five year warranty so you need to replace them fairly often vs air where you just blast the dust off.

If you are running a CPU that can routinely site over 200W under heavy load the AIO's can make sense.

I bought a used pre-built HP Omen gaming PC during the GPU price madness. The CPU is liquid cooled and the whole thing sounds like a jet engine under the slightest load. I've never owned a liquid cooled PC before, and this one is by far the loudest I've ever had.

Why did the PC liquid cooling segment redefine terms that have been used in HVAC for over 100 years, with worse definitions?

A real ‘closed loop system’ is a chilled water loop with no evaporative cooling tower.

A real ‘open loop system’ is a chilled water loop with an evaporative cooling tower. The loop is open to the atmosphere at the cooling tower.

What the computer cooling industry calls a ‘closed loop system’ (a refrigerant based cooler that comes with precharged lines) normal people call them ‘a closed loop system with pre-charged linesets’.

Split A/C units often come with precharged linesets that you just plug in to the condenser and evaporator (air handler) without having to charge the system with refrigerant.

Now, for some on-topic commentary. If you put together what I will call a closed loop system consisting of tubing, water blocks, a pump, and a remote condenser, it could potentially be almost silent. The only things that make noise are the fans and pumps and those can be located anywhere you want with enough tubing and refrigerant. If you’re trying to dissipate 1kW of heat, it’ll be a lot easier with a heat pump than with air.