Flying Schools are Flying schools....well almost.
Sure they can all offer different environments, but the most important things to look for are
1) Instructor Stability...can I fly with the same person each week, or am I going to be shuffled.
2) Can I relate to the instructor? If you think the instructor is a knob, then what you will learn each flight will slow you down.
The greatest School on the planet may not have an instructor that you can work with. (same goes for Schools/Teachers...the younger members here thinking about it could probably relate better than us old fogies)
I moved schools after completion of my training. When I next met with the owner of the original school he asked me straight about why I moved....I told him straight as well, that it was all about the instructor. When I told him who had taken over my training, his response was that he wished that person worked for him, and that he was probably one of the few suited to my personality ....
glenb makes some very valid points as well....not all schools will accommodate students lounging around to study. some will encourage it, others will let it happen, and hang around qualified pilots will help out just to talk aeroplanes...as what happens where i fly now