GTA IV exclusive content

[Bodhesatva]

Can someone explain to me how the different versions of GTA IV are working? Because from what I can tell, the 360 version is the definitive one.

http://www.1up.com/do/newsStory?cId=3160231

As you can see here, the "GTA IV Episodic content" remains exclusive to the 360. That seems... like a big deal. Is there something I don't know about? I'm not a huge GTA fan, so there could be something very improtant I don't know about. My interest in the subject springs from my interest in console sales, and how this might affect the 360/PS3 competition for marketshare.