My dd just started gymnastics and we have only been at her gym for about 6 months now. So far we love it! I don't know too much about the size in comparison to other gyms in the area. The only big name gym near us is Hill's Gymnastics (Dominique Dawes and Elise Ray).
I can definitely say from the cheerleading experience that smaller is a better fit for us. We started out at a VERY small gym for cheer (about 30+ athletes) but it seemed like it was too small for her--not much opportunity to expand, grow and try other cheer positions.
We then went the opposite extreme, a VERY big, well known gym (200+ athletes) and very well-known throughout the country. That gym was just too big. Although my dd did well for the team she was on, the gym lost a lot of the personal feel and family atmosphere. It was somewhat of a "cheer factory" where some kids were just a number and got lost in the shuffle. My dd was successful there in what she did, but I realized that just because it is a big name gym doesn't mean it is always the right fit for you.
When we switched to gymnastics, I had researched some of the other area gyms and found that our current gym was a good fit. It wasn't too small where she wouldn't be challenged, and it wasn't too big where she would feel overwhelmed or "lost" in the shuffle. Plus, when I went there to "check out the place", I got a really good feeling. My dd's coach was actually running a birthday party at the time of my visit (it was a Sunday afternoon), and she took the time to talk to me and my dd for about 30 minutes. I had originally just wanted to run in a grab a flier or a class schedule that day, but it turned into a really great first impression.
Oh, and today DD had her usual Saturday morning practice from 9am-1pm and then I usually just drop her off at 9am and go home and catch up on chores. So, when I pick her up a little before 1pm today, I learn that DD was the only team member there from her level. There were quite a few on vacation and I think one was sick (there are 7 on her team). So, the coach had pretty much given her a 4hr private lesson!!!! Pretty awesome, huh?? She could have easily called me up and said that she was cancelling practice because no one else was there, but she didn't. She worked with her the whole 4 hrs one-on-one. What a great caring coach!!! I just had to share that story because it blew me away that she would take the time for just one kid.
I'm sure the really big gyms like WOGA and Cincinnati's are awesome and it would be cool to do camps there just to get the feel for it, but I think that the smaller gyms are a better fit for us.