It's all a compromise, and different between individuals.
I would personally take the following considerations (in order of importance):
- Location (distance from home)
- Total cost (if ground school fee is high but aircraft rental is low, I'd take it anytime compared to the other way around)
- Number of aircraft (of the same type I will be training in. No point going to a school which boasts having 5 different types of aircraft - that means you only have 1 aircraft to train on. That will mean lesser chance of availability due to other students or maintenance. I'd rather go to a school with only 1 type but has a number of it)
- Quality and availability of instructor (I know there are good & not so good instructor. Even if I get a not so good instructor, I'll take my own initiative to learn)
But remember, the above order is MY preference, yours could be different...
As for type of aircraft, I don't really bother, but I would prefer one which is cheap and there are many of that type in other clubs, just in case the club I learn in suddenly closes down...
One more thing - it costs a lot to get your PPL. It is going to continue to cost you $$$ AFTER you get your PPL if you want to keep it valid...
So unless you aim to make flying a career or at least make some money out of it in the future (where you need more than PPL to be paid a salary), you better have a deep pocket!