For me, it's just the overall controls feel tighter, the tactical element with medics is much more strategic. The world is a dark fantasy world of military technology as opposed to the real world basis of the COD series. That doesn't make it better, but it sort of feels so sleek and well fleshed out in it's futuristic enviroments, that in some ways it's feels like a much deeper game than I've played before.
The layout of maps are more imaginative than most I've ever seen and there are so many places and spaces to laucnch attacks from that you'll never feel safe.
Graphically it has it's own style and it's very consistant. It makes you realise that if the same graphical style is rigidly used throughout a game, it creates a more thorough and believable world. Sonically it's as good as any other game, but has some nice extra touches, as I believe that the gunfire sounds more 'real', at least to me.
Communication in game is well implemented and seemed to work flawlessly, unlike 90% of the games out there. The amount of options and settings exceed what you'd usually get in a game of this type also.
Finally, it plays really f**king well. I did need to use that expletive. I feel fully in control playing this game. My player stops on a dime and doesn't move in the slightly slidy fashion that can happen in other games of this type. You can run through a map with more ease than usual. When you line someone up, it feels much tighter and easier to get a bead on your enemy. It doesn't feel over-sensitive as some ***les do.
Weapons do the right amount of damage, thats another important thing. I hate feeling like I've been blown away in .5 of a second. You can get hit and if you are really quick get away and recover enough to take your assailant down. Sure that happens in other games, but feels more right here.
So anyhow, thats my take on it.