Are women more emotional than men? Absolutely Not. Both genders have access to the full emotional range of human emotions. The only difference is that through gender/social-conditioning; it is more socially acceptable for women to "display" their emotions. Therefore women are better able to "display" emotion than men as they've had more practice in doing so.
I think there's a lot of truth in this. It also appears that males and females react emotionally about different things, at least in the culture I grew up in.
But it's really difficult to prove that one gender is overall more or less emotional, even ignoring cultural elements. I've been through a few adventures of my own, where I thought I was the more emotional person by far, between me and the woman I was dealing with. But much later, looking back, I realized that the woman was expressing emotion differently. So now I don't know anymore.
Mostly, I think it's important to ask WHY someone wants to decide who's more emotional. What's the end game? I've seen people who asked, because they wanted to claim that because they thought women WERE more emotional, that women were more honest. And I've seen people who wanted to say that for the same reason, that women made less reliable leaders or whatever.