Hmmm, how interesting! I definitely think differences in female organisms have some effect on behavior, but what those effects are is difficult to tell. And there are a lot of differences--I mean, girls' orgasms aren't necessarily just more intense, but I do think there's a far wider range in the level of intensity, and there's the difference in the number girls can have and what it takes to get them there and even in the evidence that they've had one.

One reason I lingered on Spock here though was that Spock was the one whose orgasm was going to be different, so it was his both of them focussed on. If Spock had always been a woman in this, the writing wouldn't have been so wholly focussed on his orgasms, I think, because Spock and Jim would be equally interested in each other's. And I like to think that if Spock had always been a girl, his behavior sexually with Jim would be much the same as it is when both are men. I.e. not very much cuddling/emotion. But of course there's no way to make that call.

(But. That does make me want to write a fic in which always!a!girl!Spock gets switched to a man, and acts the same as submissive/emotive as he does with Jim in this when he's a girl. ...I need to be stopped.)

Thanks so much for giving me thoughts to think, and letting me know this worked for you. I was pretty nervous about sharing this!