B) if a women were raped, and gained some incidental and fully unintentional physical pleasure during the course of it (which, I believe, does sometimes happen), it seems wrong to excuse the rape over that fact, does it not? One can become physically aroused when one mentally absolutely does not want that to happen.
I'll also note pregnancy as, to my mind, the most legitimate difference between the two. As for penetration, a true value for the sexually inexperienced, but I think men probably have a bigger issue with that concept than sexually-experienced women (this is my assumption, as a man). Straight men find that concept foreign and terrifying. Women and/or gay men express their sexuality in that way as a matter of course. I don't know that they'd be as scared if it as an idea, at least not after a few sexual experiences.