The most important things about searching for a good martial arts school you seem to understand well already:
-Find a school that emphasizes training for defense, not sport
-Find a teacher who has a wide background of experience, and isn't narrow minded by "My single art is the One True Way"
-Make sure the advancement system is for serious progress and not a black belt mill.
I think ANY teacher can be beneficial if he is smart enough to (as Bruce Lee put it) "Absorb what is useful". With that in mind, I don't think the particular system is so important as the individuals making up the leadership of the school. The top dog may be fantastic, but if all his senior students are coattail-riding sorry wannabes....
With your experience I would try something I hadn't learned before.
Hope I helped.