Not much of a difference and was clearly made to make this game a trilogy.
I found storymode to be a bit of a pain at times. I think it was the second level, I would be hit randomly and it was always from crazy spots on a roof. Now this game isn't hard, you just have to know where the bad guys are to kill them. I just found it ridiculous that this game was created simply to make a third COD Modern Warfare. Special Ops isn't even a big deal either. What, all they could think of was having you redo the levels in campaign?
Also what is up with no splitscreening online? If you can do it in Gow I am pretty damn sure you can do it for a FPS.
The gaming industry only cares about selling copies of their games and can care less about pleasing fans. I would return this game if it wasn't for my younger brother.