This is my first time building a PC, and I am considering an overclock later on. My CPU is an Intel i7-3770K with a base clock speed of 3.5GHz, and an ASRock Z77 Extreme4 Motherboard. I would like to do a pretty high overclock, as high as a noob like myself could get it. I was wondering what CPU cooler I should get if I do overclock. I would prefer water cooling because I like the way it looks better, but if high-end air cooling is better, i might get that too. I am not, however, going to make a custom water cooling loop because I don't want to spend that much money. also, My case has plenty of space for a large air cooler, it is an NZXT Phantom and I doubt I will put the 200mm-230mm fan on the door of the case.
From a value perspective, air coolers are far superior to water-cooling; that's largely due to the fact that they're a lot more expensive than most air-coolers. From an absolute-performance standpoint, there's not a lot that beats out closed-loop coolers - see both ofTH's benches, as well as FrostyTech's latest charts.
Liquid coolers are not quiet, though - if you want quiet, you'll definitely want something like the Noctua NH-C14 or Tuniq Tower 120 Extreme, if you're looking at the high-end of air-cooling.
I couldn't find any benchmarks that tested 1-fan and 2-fan configurations with it, but depending on your case's airflow and the fans you use, it'll probably drop the temperature by a few degrees. Simply put: if your temperatures with one fan don't worry you, then there's no need to add another.