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 ge

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.