What matters more than the company providing the course is the instructor you'll actually be working with.
You need someone who's knowledgeable, experienced, engaging, able to answer random questions on the fly, and go off-script to address the actual needs of the students.
You also need an instructor who can strike a balance between the needs of the "slower" and "quicker" students. Unfortunately, most classes contain students of all different ability levels (people shooting for simply 150+ and others shooting for 170+). In a class, you need an instructor who doesn't cater solely to one group or the other.
Ideally, if you take a course, you should be able to speak with the instructor before starting the class, get references, and sit in on a sample class actually taught by that instructor.