Guys, let me explain something. I'm not a fanboy, I'm just going to go by pure facts.
The 360 is going to cream the PS3 in the GTA IV scene. I'm not saying the 360 owns the PS3, I'm saying for GTA IV it does. Here's some things you might want to know:
Microsoft will not be releasing any downloadable content for the PlayStation 3, not after Microsoft's deal.
The 360's controller rumbles. They couldn't include it in IV because it would interfere with motion sensing.
Live, believe it or not, is a much better service than PSN, thing is is that PSN is free. Xbox Live is $50 a year.
The 360 is receiving at least two downloadable content packs. They will be a huge add on Rockstar says, each of them.
Now, the only thing that I've seen that's good about the PS3 version is that it has slightly sharper graphics. The shadows are also nicer and little details like that are noticed though. I wouldn't judge it by that though.
Those are all FACTS, besides my opinion on Xbox Live. I stand by my opinion on that, I know Chris has the same, it's up to you though.