Male vs Female Models

During our events, a number of discussions arose concerning a general desire to paint the female nude more than the male. Interestingly most of these discussions were between women and not men. The only male artist to say something simply said he'd wait for the female model to pose. Although he didn't say that he preferred painting women, I would assume that that was what he meant. So why is that? Is it just the fashion of the day? After all, it's well documented that in Greek times most models were infact male even if the female form was being represented because in those days, men were seen as more beautiful.
In the above painting, Jenny Saville has chosen to push those boundaries further, by creating a painting that represents the human figure between genders. I find this image both disturbing and compelling to look at. The figure is beautiful, very feminine possibly describing her inner feelings but essentially the body is male. The Naked Shed events questioned models experience in terms of gender but what's it like for someone between genders? What do you think?