This late into the lifespan of current gen consoles I'd go for Xbox, seeing as the upfront console price is cheaper and you'll probably only have it for a year or so until next gen.
The ps3 and xbox aren't that different. There are 4 major points to look at though: 1. The ps3 has bluray
2. The ps3 has free online, although Xbox's online is disputably better (early DLCs, party chat, larger community)
3. Exclusives. Xbox has kinect, halo, gears of war, and a tone of cool arcade games
4. What console your friends have. Probably the most important aspect, games are way more fun to play with friends, so if all your friends have a ps3 get that and live without halo etc.