Wasn't there a thread about this already? The exclusives...both systems have great exclusives. A lot of DLC comes out on xbox first in advance, xbox can interface with your computer (ps3 cannot) and has a lot more connectivity that way (i.e. streaming songs from your comp to xbox). I personally own a ps3 because:
1. blu ray player (dont have one)
2. free psn (dislike paying to play, plus I'm not big into multiplayer anyway)
3. my personal opinion: ps3 is a more reliable system
4. blu ray video games means never switching discs
5. I like the controller better
The graphics are better on one system or the other depending on the game. You'll hear a lot of fanboys from both camps swearing on their dead grandmothers that their system is best. TBH most PC games have way better gfx than both systems (given the right system specs & vid cards etc)
With the new slim ps3, they never overheat or get too hot, I've never had a single problem besides some lag with Skyrim. I wish ps3 had gears, left 4 dead, was So jealous of mass effect until it finally came to ps3. Other than that, I'd go with personal preference. If I had the money I'd buy both systems. Both are also on sale right now much cheaper than I paid (probably paid 350 for a ps3, and they're like 129 now, same with xbox)
I also hear rumours of the next gen console from xbox coming out within the next year or two, but ps3 sticks by a 10 year life cycle for their systems and will not be releasing a new next gen console any time soon (as far as I know).