Xbox 360, or a PS3?

[Nayrman]

MGS4 isn't going to the 360 ever.
The game takes up more than a standard DVD disc, and almost takes up the entirety of a Blu-Ray disc (hell, the japanese VA had to be taken out to make room for the English VA's). Also, it's one of the few games that takes advantage of the Cell processor (atm anyway).
So, unless you want the game to be about 3 discs, a hit to the graphics, and most likely some gameplay cuts, then it'll never go on the 360
(not to mention the game has some in jokes about the PS3 in the game itself)

[Jono2]

you forgot Gears, Gears 2 and Tales of Vesperia for the 360.

[The Seventh]

Get a 360.  Despite being the more fragile out of the two (besides, I've had mine for over a year and no problems).  However, you'll want to keep it in a well venthilated area, and maybe have a fan on it.

At least it has more good games on it and the online service has people and is pretty good.