It's not very often that a PhD in pain actually comes in handy, so please forgive me for coming in and pretending to have a valid opinion:
Essentially, try and define pain. If you can define it you can measure it. Unfortunately, there really is no real measure. Worse, pain has actually very little to do what is causing the pain. http://www.bbc.co.uk/news/health-12480310
Myself, I think a lot has to do with the memory of pain-- how we think about the pain, and how we remember it-- so someone's statement about labor pain being less, because women forget it and have another baby. This is helped an enormous amount by hormones. Sorry to dismiss the argument of centuries.
I can't say I'm not a little sad women are winning this one. Somehow, knowing the how many more males there are to females on this board-- it seems somehow that we all don't think much of ourselves and think there must be more to the human race than the poor specimen that we are, ourselves. Either that or the people of BCB will just argue anything.