Why is it that MW3 didn't have a multiplayer demo available at E3 and Battlefield 3 did?

Is Activision and Infinity Ward not so confident in their product that they have to hide it till the day it comes out? Why is it that Battlefield 3's multiplayer gameplays are available on youtube but MW3 doesn't? Makes me feel really weird about MW3. I have been a big COD fan but I'm really starting to question myself. Anybody feels the same or thoughts? (I just started my first Battlefield game 1 week ago!:battlefield bad company 2 & I have been a COD player since MW2) Initially I had my money on MW3's preorder but lately I've been leaning towards BF3 now. I go to school so I can't get too which would be way too much time consuming.