Pillow talk says this may be conjectured, but not completely known. 'Tis better to give and receive.
Men ejaculate (not to say that women can't, but they rarely do). Also, female orgasms last longer, for the most part.
I was thinking rather of the sensation, which would include duration.
Describe the sensations you feel when you orgasm, I'll describe the sensations I feel, and we can compare.
More seriously, though, both sexes undergo rhythmic contractions of reproductive structures. In the female orgasm, the uterus and outer third of the vagina contract, but the inner two-thirds do not. Although the female orgasm typically last longer, it only has one phase, whereas the male orgasm has two. The first phase is emission, in which the glands and ducts of the prostate and vas deferens contract, pushing semen into the urethra. The second phase is expulsion, in which the penis itself contracts, pushing semen out of the urethra.
women don't have refractory periods, men do, so women can have multiple orgasms, one after the other.... with the right partner or tool.
http://www.indiadiets.com/sex_guide/his_sexual_response/Male Sexual Response Refractory Phase.htm
As far as I know, it is at least possible for men to have multiple orgasms (and there is anecdotal evidence that it happens every now and then). What is not possible are multiple ejaculations without a refractory period.
The next best thing to simultaneous orgasms (which are unfamiliar to me) would be the dedication to climax one's partner with physically, emotionally and spiritually intimate empathy. That is, strive to learn what raises the other's passion through one's heart. This sharing is not only stimulating, but eventually emulates one's own stages of orgasm.
I have often wondered if the heartbeat affects significantly the rhythm of orgasm through its pulse.
Simultaneous orgasms really aren't that difficult to achieve. If the woman can't orgasm from intercourse alone, try a position (either from behind, or with the man standing and the woman lying down) in which the woman can masturbate. Then it is simply up to the man to work himself up and hold off until the woman is ready. Going over calculus formulas in my head works for me.
Separate names with a comma.