Whoever expelled less energy outside of the house on a given day. If equal, the role should be shared.
When you are out in the world working, the home is a place to rest and not have even more troubles. If you don't work in the world, you should maintain the home so the person keeping the roof over your head can rest and continue to keep the lights on.
In general, I think women suffer less doing the task than men do (in general of course), and they should do these things because it is easier for them.
I am genuinely curious, why would men suffer more if they did the dishes?
I'm with SweetMorningDew--a guy who does domestic chores--and voluntarily!--is definitely a turn-on.
I've always worked, so I believe household chores should be divided (unless he stays at home and didn't work, then I would expect that he would take care of the house.)
My husband-at-the-time and I were broke college students who were both working and going to school, so we split the chores (I mowed the lawn my fair share of times, too.) When one person cooked, the other one did dishes. Since I did 99% of the cooking, he did the dishes a lot, although we often wound up doing them together.
I still follow that rule, even if I'm invited to someone else's house for dinner. After I eat, I quietly excuse myself and go to the kitchen to start doing the dishes. If it's just myself and a host, we usually wind up finishing them together. But if it's several people, I love it when the host later comes into the kitchen... and is completely shocked to find all the dishes done. (I'll also dry them and put them away if there is enough time, and if I can find where everything goes.)
P.S. I have to admit that I love good old-fashioned manners. If I cooked for a guy, I'd be wondering if he was going to offer to do the dishes. If it was a special occasion, no problem, I'll do everything. But if it was an ordinary day where we had both worked, and/or I cooked for a him a couple of times and he seemed to expect me to do everything... I would definitely stop offering to cook for him.
Now of course, if we got married and I wasn't working as much as he was, that's a different story. But as long as I'm working too, I'd expect that he would voluntarily take half the chores (and not just all the easy ones!)
Responsibility is another major turn-on.