I've been taking classes since I believe about 1988 or so. I've taken courses for NAIFA, AIREA, SREA, AI, the Columbia Society (local organization), McKissock, and a local proprietary school, plus additional organizations for my salesperson's license. Hands down the best courses were through AI and their predecessors (AIREA and SREA). It wasn't just the teachers, it was the course format. The qualifying courses are taught as if they are college courses, the material tends to be taught in greater detail and to a greater extent, and the tests are difficult because one must know the material inside and out. If you want to see the difference firsthand, compare the failure rates on state exams to where the students took their education.
Generally my CE is taken through AI, simply because my education has been geared toward the commercial end for the past several cycles. They have courses that others don't have, and they are very informative.