I've only played BF2, but I LOVE that game. Looking at MW2 descriptions and videos vs. those of BC2, IMO there's no competition. Sure, MW2 seems VERY fast-paced, but all the firefights appear to be over 0.2 seconds after they began. In BC2 it seems to be at least a second.
EDIT: Also, in MW2 there appears to be no teamwork, and little to no strategy. Just the ability to revive teammates, and the larger maps give BC2 (or even BF2) both teamwork and strategy.