Alot of XBox games are already out for the PC. It's kind of a poor man's gaming PC. But PS3 has alot of games specifically for it, though alot of game developers go for all four. I'm a PS3 person, myself, for that reason. There's just more of a choice of games which I can't already get for my PC. Plus I can contribute to this team's folding@home with my PS3 when I'm not gaming on it. But XBox does has it's pluses. It's really something you have to research. And you also should check on what most of your friends game on - because if you're playing on a PS3, you can't do multiplayer with friends who own the XBox360 and vice-versa.
Either system you get, though, I'd advice against using it to watch movies. Watching movies makes the drive spin constantly and wears it out fast. It's why you see alot of dead systems floating around out there. When playing a game, the drive only spins while reading new data.