Oh ye it does.
Running multi monitors doesn't entitle you to writing your inadequate imho
and there is no such thing like "the same" between these cards. One card is quicker in higher resolutions, other in lower. One quicker in one game, other in another. One has 1.5 times the memory of another, sometimes it helps.
So there's no such thing like "the same" unless you are testing only in BF3, which is stupid.
Do you actually run multi monitors or have tested it over a number of cards / games?
Heres a quick clue, I have.