Male here, and I have a couple thoughts...
First of all, I think women use the restroom to remove bodily waste...(or shit and piss for you hyper-masculine types). I also think that the mirror provides allure to those who are concerned with their immediate appearance. As well, I think women use the rest room to rest, recollect themselves, even gather advice from their peers.
Now for the men, I have a few thoughts buffered with a few questions. First of all, men in america, both gay and straight, are often afraid of the stigma that comes with being identified as gay. This certainly cuts down on the bathroom chatter. Although urination is a natural thing, I think most woudl agree it is still mostly a private affair, and to be too socialble and familiar in a public restroom is like bringing strangers into yoru personal life if only for a moment. Rest rooms are off to the side and hidden away for a reason. Now, with that being said, I one time received a joke email about urinal etiquette. I found it pretty funny. Basically It broke down how you should approach and use a set of 6 urinals depending upon their current usage.
In my next post I will try to reproduce this...or give a link.