If you are really into games, PC is the way to go! There seems to be more of a variety of games out there for PC than Mac, haven't checked in a while though.
If you can afford to upgrade your PC from time to time and use carry over parts, hard drive, mother board, memory, etc. the PC is the way to go. I never heard of anyone building a Mac from scrap.
Stability shouldn't be an issue any more, WinXp, Win200, are very stable OS's and as stable as OSX from what I heard.