Game Informer May Issue 169 pg 51 of their 10 page article of GTAIV

"Both versions of the game will likely be identical, but Rockstar has confirmed that downloadable content will be exclusive to the Xbox 360 Version. This content is said to be sizeable, and when asked about whether or not we would see this impressive new take on Liberty City Living on past one game Houser grins and says one thing "episodic content".
Though regardless the 360 version would be better just for the simple fact it's not on a Sony console.:thumbsup: