I would say the style that suits me but also the instructors ability to teach is very important. I guess for me a few of the above cant be seperated
One of the main thing for me...personally....is the instructor. His attitude, his qualification being that he knows what the hell he's doing and what he's talkin about. His teaching method. Over all, the instructor. That is what is important. A good instructor would have his stuff in order. His student's attitude and all.
The syllabus is what you are going to be learning, ergo it is the most important thing. I basically just turn up when I want to spar and my crazy shotokan brother or friends are away, so maybe I should shut up...