My point being that if they are both drunk, neither can "legally" give consent.  His body may consent, but did his mind?  Is he going along because it's expected of him?
So, should both be charged with rape?  Or neither?  Or just him, even if she's the more sober of the two?
I'm all for throwing the book at perpetrators of forceful, violent rape, just as for any other violent offender.  But the non-violent instances, especially when one recants days later or when reported by a third party, become less clear.