If you get a 360, don't get the Arcade bundle, it doesn't come with a HDD. I'd get the elite if you can find one, it has the largest HDD, and is the only system that comes with an HDMI cord. I think the value is there. I think all of the Xboxs come with HDMI out now though, they didn't used to.
The only real reason why you might not want an Xbox is because of the high failure rates, which are, well they're very high. Just know that when you buy it, you're not much more than a coin toss or two away from it bricking, and having to send it away to Microsoft for a few weeks.
I love my PS3, but it's also my Blu-ray player. Just on the gaming side, I also love it but I'm a very casual gamer. I find the online perfect for me, it's free and does anything I could want. You can't download movies or TV shows like on Xbox live, and the community isn't the same (live is more "youth centric"), but online gaming with Playstation Network works perfectly, and that's all I really ask.
for games, If you get an Xbox buy these
Halo 3 (shooter, duh
)
Mass Effect (action RPG)
Bioshock (shooter)
Gears of War (shooter)
If you get a PS3 get these;
Uncharted (adventure game, like a modern Indiana Jones)
Gran Turismo 5 Prologue (racing simulator)
Ratchet & Clank (a cartoony action platformer)
Resistance (shooter)
If you're into oldschool RPG's like Final Fantasy, you can get Folklore. I can't stand the game type but those who like it love Folklore.
And these are multiplatform titles, so get them for either one
Burnout Paradise
Call of Duty 4
Oblivion
The Orange Box
Guitar Hero or Rockband, good party games
Devil May Cry 4
uh.. sports games? I don't play sports games.