I've helped a lot of people navigate materials from both of these companies, as both an instructor and curriculum developer at MPrep and as an independent tutor who helped students who were using TTP (and other) materials. I will say that while the TTP materials are "thorough," I think the MPrep resources are better suited to self-diagnosis and applicable strategies, particularly for Verbal. You honestly might be able to just get away with purchasing the MPrep verbal book and then using official questions. TTP doesn't provide practice exams, but neither does MPrep anymore (although they do purchase the access to the official ones and the official guide for you if you purchase a course or tutoring, but that's a much bigger $$ purchase). And I'll stand by my personal feeling that no one mimics official verbal questions all that well (yet)!