I found this interesting, so I filled out your survey :]
I rarely choose to play a female character. Usually if I do, it's because they've allowed me enough room to custom tailor the character to my specific tastes. As a female gamer, I still feel like most games are created to suit a general male preference. For instance... seductress type females- or butt-kicking, muscled, small waisted, big boobed type females. So I guess it really comes down to me not being able to relate on an aesthetic level.
And since I can't relate to the female anyway, I don't see how playing a dude is any different.