Straight women are least likely to orgasm.
"The study, by Indiana University, Chapman University and Claremont Graduate University, showed the proportion of people who usually orgasmed was:
- 65% of heterosexual women
- 66% of bisexual women
- 86% of lesbian women
- 88% of bisexual men
- 89% of gay men
- 95% of heterosexual men"
I don't think I've ever not orgasmed (not through PIV though) with my partner, and we've been together 9 years.
I've seen some women claim they don't mind not coming that often and still like sex because of the "closeness". Fuck that. If it was happening for me less than half the time, I wouldn't be with him.