That's a tough one. On the one hand, consoles are considerably cheaper. One system every 3-5 years, all games are guaranteed to work on it that carry the console logo. Downside is that consoles suck for FPS games. Great for almost every other kind, except maybe RTS.
On the PC side, you'll be in a perpetual, and expensive, upgrade cycle. RAM, video card, processor, power supply, even hard drive... You'll be forever upgrading these things, and it will start to add up pretty quickly. The up side is that you can't beat the PC for FPS games. Some people do get quite good with console controllers however, so...
I will say that the PS3 will let you connect a keyboard and mouse to use in game, if the game supports it. The 360 won't, but if you can get the games you want on the PS3 that might be an option to think about.
If it were me, I'd go with the console, but then I got tired of FPS games a long time ago. They're all pretty much the same when you get down to it. Run around cramped narrow hallways, shoot lots of bad guys, pick up ammo and health as you go, the end. Not a lot of actual skill required, just good reflexes. That's why I moved to RPGs. You have everything from gut wrenching story tellers like the Final Fantasy series... Final Fantasy X's ending is a real tear jerker, though Final Fantasy 8 had a few moments. There's the childish humor of Disgaea that just somehow works. And you also have games like the Shin Megami Tensi: Persona series that kind of straddle both sub-genres. A bit more strategic than FFX, but not as tedious as Disgaea. You also have some fun platformer type games such as the Jak and Daxter and Prince of Persia trilogies. You could branch out into different game genres with a console, instead of limiting yourself to more of the same with FPS games.
I have problems with deciding what to buy. I will play mostly games like farcry2, fallout 3, crysis and such. the 360 is cheap (compared to reliable PC) and i will never worry about games not being able to run on it. The PC will cost much more but then I will have the best controls with the mouse and keyboard and I will not have problems in the future when it's cheaper to upgrade the pc instead of buying a new console. Do you people know anything that I don't know that will help me decide?