I bought BF3 rather than MW3. After reading about the two I went with BF3 because of the map size and the graphics. MW3 is still on mt list but it will be a later on down the road purchase.
So far, I am delighted with BF3 in both play and appearance. Single player was a bit short- took about 6 hours, but everything with single player is sadly that way- too little content too quickly finished.
I can max it all out with my SLIed GTX 580s and it looks and runs wonderfully!
ADDITIONAL BF3 Comments: Single player -campaign- was very linear and took about 6 hrs to complete in a very unhurried manner. I think it serves more as an intro or show and tell since the jet, helicopter, and satellite parts you play as a copilot / spectator. It does have a neat story line!
Co-Op is OK where it's you and another player vs AI. But it's only got a few maps so far.
Multiplayer is great in the smaller and medium sized battles where there are like 6, 8, 10 or so players per side. Those are challenging and fun.
What I have found with the big battles with lots of players is they can be less than gratifying. There are snipers galore just outside the main spawn point waiting for you as soon as you leave the area. On foot you are lucky to last 45 seconds. You can try to run the sniper gauntlet in a vehicle. You seldom will get a vehicle with a lot of players except maybe a small truck. It doesn't really matter because no matter how fast you drive, before you even get close to the combat an anti-aircraft or minigun equipped vehicle will shred anything you are in before you can exit and try to run for cover. The spawn point is always chiked off. The game becomes die and respawn. Die again. Respawn again. Die again. The only variation is sometimes you respawn on top of another player. While it's perfectly logical tactics to cover any approach an opponent has for resupply it makes for a pretty frustrating experience in the game. When you have 20 or more players per side sparing a few to man a couple tanks and play snipers is easy. You still have a big force fighting. Kill the opponent off and prevent any re-enforcements from getting to the battle and you basically win not only because you outnumber those fighting there, each kill trying to exit a spawn area drops the count. It seems more than a bit unbalanced. The biggest battles I have tried to fight in so far have had 24 to 26 players on a side and what I describe is the result. I couldn't even imagine the 60+ per side. But, no worries really. Eventually the server kicks you off without explanation or warning.