Stagecoach does appear to be one of the more expensive ones, they also like you to buy their shoes and t-shirts, they are run as franchises so a lot will depend on the person running them, they do have a set sylabus but at age 6 its still a lot of games and running about.
Other local Drama clubs again run by individuals so can vary a great deal, some will be more full on doing plays every term, some will be more erm 'fun'. Some are very focused on acting while others involve a lot more singing and/ or dancing.
You have to figure out what will suit your daughter at her age, you need to perhaps observe a class or for her to try it out.
My DS tried one where he was at the younger end of the age group, it was all a bit to grown up for him, the one he as at now has smaller age ranges in each class but they all get togehter for their big productions, he also does film production with them which he loves.
I like that they are pretty informal they have t-shirts but you don't have to have one, for productions you might be asked to put them in dark trousers and white t-shirts but nothing outlandish or expensive, they provide the actual costumes. They also do easter and summer workshops, which are great if you need holiday childcare, I don't but they usually go to a couple anyway. DD is doing a full week of HSM or ABBA I can't rememeber which . DS is not so keen this easter as the older workshop is based on the musicals, so he is waiting for the comedy one in the summer.