According to Infinity Ward or what’s left of it, there won’t be any lead platform for Modern Warfare 3 and both versions will be running the same. While most games are built on one system and ported over to another, Call of Duty: Modern Warfare 3 won’t be one of those games.
Downloadable content will be its own distinct part of the game apparently but Creative Strategist for Infinity Ward Robert Bowling didn’t deny that that content wouldn’t be pay-for-play, which nobody’s going to be happy with. But the game's so far off now, according to Bowling, that we can't make any assumptions.
The PC version will apparently be the only one that receives its own unique optimizations of all the consoles the game will be available on. We’re not sure if this is positive or negative but usually the PC community is neglected and rightfully so.
Call of Duty: Modern Warfare 3 releases November 8th, 2011 for the Xbox 360, PlayStation 3 and PC.