I know this is a bit late(!) but I thought I would throw my 2 cents in.
I recently built a
gaming pc and one of the dilemmas I came across was around cpu cooling. My original plan was to go with an air cooled heatsink.
The one thing that changed my mind was the
rate of cooling. I could have gone for a Noctua and had a couple of degrees up my sleeve, but (for me) it came down to
how quick the cpu could be cooled after stress (constantly running my I5 @ 4.5 GHz, max temp. 65 C).
I went for an AIO cooler but the same holds for a custom setup.
A liquid setup will always cool a cpu quicker than an air setup. It is fair to say that liquid added to a gpu will do the same. Of course, the risk comes down to leaks & failures, but the advances in AIO setups over the years has improved greatly. Custom loops comes down to the care of the person constructing it.
Having said that, I recently replaced my radiator fans with a set of EK Varder high statics because the bearings in the originals became dodgy. Maintenance is something to think about. The noise is not offensive given the location of my pc on my desk.
The other reason is that I made a portable system and the AIO offers more security/stability than the weight/stability of an air cooler being moved around...not an issue for a desktop.
Whenever building a pc, stop and think..."What do I want it to do?".