Regrettably, I didn't use TopScore nearly as much as Kaplan, and myself and DAT instructors found many errors with Kaplan. This was and still is discouraging given the costs of Kaplan courses and study materials. In any event, maybe I would've found more errors with TopScore if I had used it primarily, but I doubt it. I am sure that others may or may not see it that way. In the end, I think the best study method is TopScore and old textbooks, which was the way I studied for the organic section of the DAT, and not surprisingly, was the only section I scored a 20 on. I hope this helps. Take care and GOD bless.