I was a late to playing FPS games online, the first I ventured on was MW2 and absolutely loved it. One of the most played games ive ever owned.
It was only about 3/4 months ago that my younger brother got BF2 and begged me to get it so we could go online, finally gave in and must say I really enjoyed it too even though I was adamant I wouldnt because of the difference in gameplay.
That is what is so good though, that the gameplay is so different and thats why I feel it is easy enough to own both and get enough gametime on both.
If I feel like jumping on and going a bit Rambo one night I can stick in MW3, yet if I fancy taking it a bit slower, more tactical in goes BF3
In short I will be getting both, with Fifa they are the only games i really get at full price.