Usually I'll play as my own gender for my main game (Male)....but if I get another one (like the third version) I'll play as a girl.
Just the mix it up a bit. I play as a girl in platinum. I don't see a big deal, and it makes a change from looking at the same sprite all the time (if you have two games in the trio of games)
I voted as I play as other genders though.
In pokemon black/white, it's the first time I've really liked the male character...so I'll much more happily choose him this time. If I do get the third version I'll still probably play as the girl though.