Air or Water, doesn't matter as long as not overclocking.
I'd only suggest water cooled if overclocking a system.
Overclocking a system these days is mainly for bragging rights of pushing a system to limits with crazy frame rates and get high scores - or - pushing lesser end or older hardware CPU/GPU to perform like a better or newer CPU/GPU at risk of damaging components by forcing faster clocks.
I've only been able to get a 10% CPU Clock gain before odd freeze frames and stability issues, and the stability issues weren't caused by running too hot. It was issues with the fact that the CPU can only run so fast before the CPU stumbles as transistor states on die can only physically transition so fast before a 0 or 1 isn't flipped correctly as well as the memory controller is on the CPU and has its limits and I was forcing FSB to be faster which also affects the memory controller in addition to the CPU clock.
The CPU I had, had a fixed multiplier of 13x for 2600Mhz with 200Mhz FSB setting as the manufacturer didn't intend for it to ever be overclocked and my motherboard had the ability to adjust to overclock the FSB so i was able to go from 200Mhz to 222Mhz to get 2886Mhz but with issues and backed down to 220Mhz FSB to where it would run without issues and CPU was 49C prior to OC and with overclock was running 57C gaming and air cooled solid block of aluminum with single fan for AMD Athlon II x4 620 2.6Ghz quadcore. *Others go this same CPU into the 3.1Ghz range and stable and liquid cooled but they also had to adjust voltages to over drive the CPU with greater power demand and greater risk of damaging the CPU. I didn't see it worth it to go past 2860Mhz ( 2.86Ghz ) for a native clocked 2.6Ghz CPU when another 250Mhz to squeeze out of it not worth the cost of adding liquid cooling and on top of that having to try to find voltages that worked that wouldnt cook the CPU or the VRMs on the motherboard.
I'd suggest buying or building up something that is adequate running the clock speeds intended by manufacturer without the need to overclock or go with liquid cooling unless you want something to show off to friends as look at the glowing gaming system in the corner that racks up the electric bill, is pretty, costly hardware, and risky to damage or data loss if something crashes during a write to HDD or SSD. *Most APU and CPUs these days have a built in overclock feature like (Turbo) of the Intel APU and CPUs where a 1.7Ghz CPU will jump to 2.5Ghz for a bit but jump back to native clock 1.7Ghz when extra processing power is no longer necessary.
I'd hold off on overclocks until system has aged and you are trying to avoid buying new and forcing an old dog to do new tricks at the risk of damage, but if it dies in the process at least you got many years out of it before it failed assuming you buy a CPU that is high enough end to not be already behind the times for intent of application. As thats what i have used overclocks for and the slight performance gain helped in some heavy hitting games that needed just a little more than the CPU was designed for and if I smoked it it just would make it easier for me to be like well I got every little bit of use out of it and now a reason to get new because its cooked.
