I have read studies that say men benefit more from micro-napping and therefore can handle shorter nights as long as they can micro-nap. I sleep significantly shorter nights than my girlfriend. She can sleep for 10-12 hours every night. I only sleep for 7-8 which means I go to sleep 2-3 hours after her. But I do micro-nap sometimes. If she naps it's for a long time, usually because of lack of sleep the night before. She is younger than me, and when I was younger I used to want to sleep for 10 hours or more, but when I did it messed up my sleeping pattern (gave me a >24 hour rhythm). So I'm inclined to think she really does need more sleep at night than me.

I don't think sex matters, it's simply how someone is wired.