This is a fascinating discussion. I know I've mentioned this before, but I write a bit (amateur, very bad), some of it erotica. And it is fascinating as someone who likes PIV, likes it enough to want to write about it, to set about unpicking the male gaze, the underlying assumptions about power relationships both in and out of bed, the fundamental issue of a lack of vocabulary (there is no word, barring the clinical clitoris, for the organ that is actually responsible for the female orgasm - one is reduced to twee euphemisms and work-arounds). At both extremes of the spectrum - deliberately provocative blogposts that all PIV is rape, and trying to write feminist friendly erotica - you collide with the fact that how we view sex is conditioned by a world, even a language, which takes the male sexual experience as primary and central. (Re. penetration and the excellent point made up thread about not reducing women's bodies simply to holes, I toy with alternative language about "enveloping" , etc. - trying to make women's bodies an active part of the scene rather than passive recipients).
It's also interesting as a kind of piece of social anthropology to read slash fanfiction (male gay erotica written primarily by women for women). Some of it is written I think out of despair that it is so damned hard to write a relationship of equals for a heterosexual couple - so two men together gives you an idealised way of exploring relationships without the underlying socially predetermined power imbalance in het relationships (even the equal ones - because society in terms of expectations from family, the workplace schools - whose number gets called first when the kids are ill - all this eats up enormous amounts of head space because you actively have to fight against it if you want an equal relationship). Some of it does reproduce the tropes about power imbalance - there are some hilarious arguments out there about whether one partner should always "bottom" or whether they can swap over. And some of it actually reproduces the worst sort of "Men are from Mars, Women are from Venus" tropes imaginable (so called alpha/omega slash), because the writers are so embroiled in their own patriarchal cultures that they simply cannot make the imaginative leap to see a culture which could be different. (Important disclaimer - very little if any of this vast body of writings bears any resemblance to anything a gay man would actually recognise as his own life, if my conversations with gay male friends are anything to go by).
Sorry, possibly a bit off topic, but I do think it is fascinating when you start digging into the assumptions about power underlying het sex. You can do this with the sort of deliberately extremely provocative blog post at the start, or you can come at it from lit crit, or you can come at it by asking "why is rape in the criminal justice system conceptualised from the male POV as 'how did I know she consented?' rather than from the female point of view as 'sex I did not want'). But whichever way you come at it, sex doesn't happen in some primal animalistic bubble detached from surrounding culture, it comes with all the power relationships and inequalities of that culture.