My current toon in Warhammer Online is a female, and not for any particular reason. That’s just what popped up first when I went to the character creation screen that time around. It can be annoying, especially since I play on a Role Play server, to have guys hit on me (or just down right sexual harass me) while playing, and I don’t seem to notice any of these major benefits that you guys have mentioned (even when I played WoW).
As a general rule, I always assume another player is a guy (despite the gender of the avatar) until it’s mentioned otherwise, especially if their character is skimpily dressed or running around in their underwear.