I didn't use either so can't really comment on that, but I can tell you that any data comparing the effectiveness of TPR to Kaplan isn't going to mean anything. People learn differently, Kaplan might work better for some people, TPR for others. There's just too much subjectivity when you compare them head to head. Your best bet is to look at how each company approaches prep for the MCAT, and determine which you like better. Both companies are solid, and have worked great for many people.