With the growing popularity of MMA, Kickboxing and Jiu-Jitsu gyms in the USA & worldwide, one has trouble deciding on where to train. There are pros and cons to big and small MMA gyms.
Big gyms: are very tempting to try out. "Everyone goes there" Is the feeling you get from a larger more established location. They might have a high-level pro fight team. Who wouldn't want to rub elbows with famous fighters seen on TV. Since they're already established, you can feel better about learning from a tried and tested source. Some people are just coming in for the workout and feel better knowing the place is well run and will probably be around for a while. They can have a better assortment of amenities and equipment. And of course some bigger gyms have a wider range sparring partners.
Small Gyms: Luckily for the little guys, America has an affinity for the underdog. Aside from the romantic notion of being one of the 300 Spartans squaring up against the massive Persian Army, students can feel better knowing they are getting a more personalized approach. In a smaller gym with smaller classes, the instructor has more time to spend with individual students. In a larger class it is nearly impossible to give any one student more than a few seconds of interaction. Smaller gyms have a higher likely hood of having the owner or an established fighter teaching beginner classes. Unlike the larger gyms where politics and favoritism can play a role, there is a vested interest from an aspiring professional coach or trainer to see his/her students excel showcasing their progress to a tightly knit martial arts community.