83 months ago
You could probably start by copying that entire subject line and pasting it on Google.
I agree with StressMan, you'll find lots of info on google for such a general question.
Now if you give us more info, perhaps we can be helpful. For example, what are you planning to cool (CPU I'm assuming), are you planning to overclock it, if so, how much? What kind PC build are you aiming for? (CPU, GPU, case,...).
This is a complex question that depends on your intended build and use case.
Let's assume you use a socket 1155 CPU, like the 3570K or 3770K which are standard high-end gaming PC CPUs (the 3570K is enough for gaming, games never use hyper-threading and few other applications do).
I will make one comment, which is that for low overclocks (e.g. 4.2 GHz or less), air can actually be much quieter than water, especially cheap water kits. Do the research and spend the money (like ~$20+ ea.) on higher end low-RPM (400-1500) fans, like Noiseblocker M12-PS, Noctuas, Corsair SP120 Quiet Ed., Scythe SlipStream, ThermalRight TY-140, etc., and a massive heatsink like the Venomous X / Super Megahalems / NH-D14 / Silver Arrow, and you have a solution that is far quieter than any off-the-shelf water kit (and still cheaper than the highest-end water loops while being just as quiet). You'll run ~65-70°C at full CPU load, but that's well within the thermal design of the chip, so who cares if water runs 10-20°C cooler? Those CPUs can run at 70°C forever with zero downside.
Now, go for a big OC, like 4.7 GHz+, and water is the obvious choice. Air cooling at that rate would be ridiculously loud compared to even a basic water kit like the Corsair H55 or even better the H80i (which is a decent kit BTW). And water will wrangle those temps down far better, which is important with such high OCs.
My two cents.
Keep in mind that as long as you hit a certain CPU speed, gaming framerates are FAR more dependent on video card than clock rate. OC is awesome for myriad tasks but with a high-end CPU it's not usually the limiting factor on game performance.
Well are you wondering if you should get a full loop or a closed loop? I would honestly recommend a cheap air cooler, you can always upgrade, but a cheap 20 or $30 212+ will do just fine temperature wise.
H20's the way to go!