That's the thing. I can't think of a single trait that is preferable for men to have but women not, or for that matter, vice versa.

I used to be a gender abolitionist, and the only reason I'm not is because I can see how much it means for trans folk to represent at the gender they identify with. (I also hypothesize that it's similarly important for self-identified alpha-males, who just don't feel masculine enough no matter how much they try.)