I can play either one but it all depends on who is in the group. If there are some ladies playing to (a rare ocassion) then I'll opt for the same sex character since the ladies always want to play with the female character.
For me I will definitely choose male if I create an character on a RPG, it is possible that I can play a female character but I find that a big challenge and unique role-playing. I will rather stick with male when creating characters since I am more 'partial' with that.