I've seen the men coming and going from Gold's and they are pretty much the same fitness and gym crowd as 24 Hour Fitness (where I go).
Perhaps there is a separate "Porn Star Entrance", so I don't know if inside it is hotter than what I see releasing onto Market Street.
I prefer 24 Hour Fitness because I had a membership when I moved here, and I only pay US$79/year. Yes, per year. I also have my free choice of any of the 24 Hour Fitness gyms around the U.S. (Up to the Sport category).
If you're visiting, you might want to do the Gold's thing just because the gym seems to be bigger and more fully equipped than the 24 Hour Fitness which is located in the Castro.
I like when my gyms are bigger and more fully equipped.