Which is better Cpu Cooler ?

Why not Water cool?

They both work in a similiar way, and a closed loop can offer you a easy to use solution.

They both involve sticking a copper plate onto the processor, which pulls heat away from the CPU. water cooling is just more efficient.

WC is alot better at transferring heat away from a hot component such as your CPU, rather than just pushing air onto it/across it. another big bonus is the quiteness!

LArger air coolers have become godlike at thier job, even with OC cpus, the massive benefit of using a watercooling system is that it quickly returns the chip back to its idling temp, once you stop stressing it. This is good for promoting life for your CPU

Not argueing closed loop or open, as they each have there specific pros and cons, but closed is the easier of the two! (plus no leaky shakey hands spilling all over your lovely components!)

One loss of watercooling, is that air cooling promotes air movement within the case, but a few case fans, or a push pull system on the radiator can fix that right up

Some recent coolers worth looking at

DUAL RAD:
Seidon 240M (coolermaster) £73 - concerns over the fit of the bolts (read into this) - but is a fantastic cooler, especially for OC'ing. (93/100)

Water 2.0 Extreme (thermaltake) £103 - a quality cooler, although another awquad mounter. Quite pricey for what your getting (86/100)

ELC 240 (Enermax) £83 - Effective and incredibly quite cooler, but not the best in performance (87/100)

h100i (Corsair) £90 - Quality cooler from corsair, on default setting it lacks top performance, and has the lovely corsair link software, good if you have other corsair components (I have this cooler, and the h60 aswell, Brilliant looking aswell) (87/100)

SINGLE RAD UNITS:
LQ310 (Zalman) £46 - A single Rad unit, means has to work a little harder to do the same as a dual rad, and has a dodgy system for mounting which can be a nightmare, but for the peak performance too cool :/, it scores quite well. (89/100)

H60 rev.2 - £60 - Nice mounting system, prob easiest to fit. doesnt have link intergration (shame )
Very quite even at 4.5ghz running 100%
Corsair loyalists will snap this up, but there is cheaper better units out there
79/100

Hope That helps a little