I've always preferred FF-servers, for every mod I've played. It keeps the players sharper and more alert, more aware where they're firing, and just makes for better players in general.
Of course it also means you'll occasionally get shot by your own teammates, but they'll get better eventually. And besides, the opposing team suffers the same thing as well.
All in all it really shows who can differentiate between correct targets quickly, rather than just being a twitch-gamer and shooting anything that moves.