I think that MW3 and BF3 should not compared against each other, instead of previous versions of themselves. I hopped on the band wagon of Bad Company 2 when it was on sale on STEAM for 8$. And, I'm happy I jumped on the wagon.
It took getting used to, I had to change my tactic from CoD4 run and gun to team play and objective oriented. But, I am slowly starting to enjoy Bad Company 2 more and more, than CoD 4, which has been my life for a year or more.
BF3 is a better game than MW3 because it is not a reskin. Then updated the Frostbite, weapons, player animations, and a lot more. Yes, I am no expert, but Call of Duty series has gone to Activision's mind and it is going to be a money maker. Look at the past. MW2 based off of MW. I mean, come on! Are you stupid? MW3 IS MW2. (Similar, imho to L4D2 and L4D).
But, I'm also sorry to say MW3 will most likely outsell (which is the one winner in today's world: profit) BF3. Oh well. So, please stop comparing BF3 to MW3. We smart people know MW3 is just a remake with a new name