Some of the pros are they have numerous teacher's and if your teacher can not make a lesson, they can have someone else fill in. It also is easier to switch teachers, if yours is not a good fit.
They have documented programs and evaluation processes.
They have special programs, shows and competitions.
Cons - They tend to be more costly.
The special programs and activities, they promote heavily are pretty expensive.
They tend to try to keep you in their competitions and shows. They also push pro/am competition, which tends to be more costly tham am/am competition.
Key point is there are good teachers out there, who will work with you to meet your objectives. If you start with a chain or an independent who is not doing that, go elsewhere.
Lot of people have strong feelings on this topic, based on personal experience. My key point is there are teachers out there who will meet YOUR needs, don't settle for less.