Some noticed that some lesbians like gay porn. They contend that the girls in lesbian porn aren't realistic, enthusiastic or pretty. They also offer curiosity about penises or revenge fantasies (watching men get fucked).
Comedienne Judy Gold humorously notes that penises offer a visible measure of arousal. This is actually interesting. The dramatization of inner states is both a staple of personal and home life (and work) and the theater, painting, sculpture and film.
Tristan Taormino is freed from worrying about exploitation by watching gay men. Thanks, but no thanks: you don't get freed from complicity in exploitation when men are cheated, suborned or brought into hustling and porn when underage.
Difference can be very exciting; this is part of it, I think. But I prefer to think of it as a triumph of imagination. Some guys love women so much they want to be lesbians. Why shouldn't some women fantasize about growing members to take even more advantage of all those lovely orifices? And what is porn but a fantasy of more?