This cover was rejected because Marvel's legal department didn't want us using the movie version of Iron Man's armor. When your work is scrutinized by committee, this sort of revision is pretty typical in commercial art. It's irritating when it happens in the very late stages like this, but as I said, it's fairly common. I was told to change his armor to the Extremis version.
I prefer this Adi Granov designed armor much more. No one can touch Adi when it comes to drawing Iron Man.