You could probably fill an ocean with the ink used to describe the difference between men and women from the rather traditional "men are stronger than women" right up to "men are from Mars, women are from Venus". What always surprises me is that it burns down to a couple of 'real' differences.
Yes, it's true, men are physically stronger than women, at least on the average and that's what you have to base every question about the difference between men and women on. Men have something over 40% of muscles, compared to their mass, while women only have a little over 20%. It's only logical to deduce from this a pure physical difference.
And yes, every adult should know that men and women are not build alike - as much as women wearing Size 0 seem to try for androgyny. I sometimes envy men for their penis, but only when I'm forced to use a dirty restroom somewhere and wish I could do that standing instead of having to hover over the seat, trying not to touch it too much. Apart from that I think that it's neither the most good looking limb of a male body, nor the best designed means of reproduction. The fact that a man has to keep some of his most tender parts outside his body is bad enough, even without us women knowing by now where to kick him in an emergency. And from what male acquaintances have told me, that's really, really painful...
The last real difference between men and women is the fact that women tend to live a bit longer than men. That's probably down to our very evolution building man to do daring deeds like hunting mammoths, deeds which will kill him off early anyway, and building woman to give birth to and raise children, which will take a good deal longer. Men are build for strength and power, but very much like a high-octane motor, they are prone to fall to pieces quickly without a lot of maintenance - which men don't seem to deem necessary.
Most things men or women point out as differences are no real differences in my view, but rather areas in which society does not handle both genders alike. Take the most common thing: driving a car. Statistics state that women do usually drive better than men and are less likely to get into an accident. Most men will tell you that women drive worse than them, especially their girlfriend or spouse. Or take parking. It's true that most accidents women are in happen in the parking lot while moving into or leaving parking spaces. This is something women seem to be worse at. Scientists claim it has something to do with men having a better eye for three-dimensional situations. But if you really look at it and talk to women who are bad at parking, you'll realize that nobody ever really worked on it with them. The way I see it it's like this: If a man is bad at parking a car, his friends take him to some parking lot or other place where they can practice this until he's finally got it. If a woman is bad at parking a car, her friends (male and female alike) only shrug and say "that's how it is". Women who drive a lot because of their job usually are just as good at parking a car then men are ... because they practice more.
Or take the idea that women are worst gossips than men. Most people will claim it's something evolutional, that women have always talked more and gossiped because their job (raising children or collecting fruits, vegetables, roots and grains) didn't demand silence. But if you really take a look at it, you will find men gossiping just as often, just a little shorter, maybe. Society has deemed it acceptable for women to stand around gossiping longer than men. Besides: under the right circumstances men will be gossiping just as much as women.