Just wanted to put in my five cents about these games, I find that personally I dislike the high-action guns blazing "call of duty" vibe that has recently plagued the series, as I firmly believe that one of my favorite first person shooters ever was CoD4, the first modern warfare. I liked it because the gameplay was more balanced, guns were more or less equals, and you didn't get really crazy awesome guns, well besides the p90 which was banned from a lot of the servers I played on.
I have though, loved the battlefield games from the start, because they were different. Their whole game style was focused on teamwork and cooperation. I find that is what is lacking from most modern games, but I remember having great times with friends, just by going through and using teamwork, and games tended to last much longer than 5 minutes or whatever the new call of duty games do.
I believe the way the games are focused builds the community, and while battlefield has focused on teamwork, call of duty has created a game where people feel like they need to get the highest score, the most kill streaks, and overall be the best.