First of all mate, whats your budget? Because theres no way you're going to get a decent gaming PC the same price of a PS3. I just built myself an elite gaming machine, and it cost me the best part of £1500. Just thought id let you know. PC gaming is very expensive, every couple of months you're going to be forced to splash out hundreds on hardware updates if you want to run games on the highest graphics settings.
One year ago I would have said go for the PC, but nowadays the PS3 looks like its picking up pace, the online features are improving and theres some very good titles out on the horizon. Of course theres no need to worry about hardware updates and the console is supposedely built to last a decade, so theres some good value for money.(PS2 has been released 8 years ago and is still releasing games today!) Oh and you get a Blu-Ray player thrown in too if you fancy some high-def home cinema
In terms of games, well nowadays PC exclusives are becoming more scarce and console gaming is very much catching up with its potential; just look at oblivion on the PS3 and Xbox 360, idential to the PC version if not better (its definitely more stable!), BioShock on the 360 is better than the PC version. Infact even Crysis is supposedely getting a console release and we all know that Fallout is also to be released on the PS3 and 360.
Go for the PS3, you'll have alot more fun with mates. Besides most online PC gamers these days play either World of Warcraft or Counterstrike (dont have a problem with the latter, just I think its horribly outdated if you ask me).