I dunno, I don't see the difference. Then again, I am a girl.
There really shouldn't be any difference. If a guy gets beat by a girl, whatever. It's just another gamer. There shouldn't be any of that "Blergh! My manhood has been compromised! I must regain my honor!" because...that's just dumb! Even if we're playing, let's say, Gears of War or Madden or Battlefield. It's as if a woman gets angry because a guy cooks. It's just dumb in so many levels.
On the other hand, as a girl, it does bother me when a douchebag beats me because they gloat and make rude comments. Any other than that, I'm fine with.
And really, if any guy feels differently or awkward because he's beaten by a girl, then I suggest you grow up/get laid/grow a pair/etc. Not aiming this at anyone in particular. Just. Saying.