I think about 14 Megabyte's are saved to the HDD for any CoD until the DLC comes out, then it goes to about 1 Gigabyte (though Black Ops made it to 4 because of Zombies if I remember correctly).

I think I was about the Twentieth to make a thread about this in the BlOps forum a few months ago. Though, I meant just loading data and what not. Figured the games, in theory, would run smoother. Like the arkham games or Heavy Rain.