I would say that statistically speaking, gay men are more vocal here and post more. The straights are here, but tend to be more quiet.
How do I know?
When the debates were going on whether to split the fictious stories section or not into, Straight, Gay, and Everything else, a poll was taken. The vote to split the stories was way skewed for the split. Now, this part is an assumption based on the comments posted, which I read everyone of them. Most straights were for the split. Most gays were against the split. Straights voted, just did not post or speak up.
If you look at the forum of the adult websites, there are always more people "viewing" in the straight porn section.
Now here is where it can get complicated. Gillette hit on this point. That is not to say that there is cross over. There are a lot of bi-men here that appreciate both. But bi-men are considered gay, and will go to both areas where straight men would probably never visit the gay porn sections.
Just an observation based on assumptions. I will admit that this could totally be wrong.
Edit: I just have to add that the only way to vote on a poll, is to log in as a member.