I don't want to buy any game outside steam, I heard something like EA "stole" players' games (BF3) and never gave them back, not even the money. If till X-Mas it is available on steam, there will be no steam players to play with. So, no.
Either way Battlefield 3 is not even comparable to MW3. It would be an insult to BF3 to even attempt to compare it to MW3. BF3 is sooooo much better.