I had this same dilemna...
So I went and looked at both centers, one right after the other. I then called both enrollment 800 numbers, one right after another. I chose Kaplan.
I'm learn better on my own and thought that being buried under all that material might be a little much for me. But that wasn't the main thing that
swayed it for me.
When I went to the Kaplan center, there was a definite professional feeling to the place.
When I went to the TPR center, the person in charge of the center met me in flipflops, jeans and a tshirt with a hooded sweatsuit type of thing over the tshirt. I was introduced to one of the instructors who looked like he'd just rolled out of bed (it was 4:00 in the afternoon) with a wrinkled t shirt, needing a shave. My thought was,"If this is the way they present themselves to potential professionals, it really doesn't strike me as an outfit that has a lot on the ball".
When I called the 800 number, Kaplan routed me through to one particular person who answered all of my questions, advised me as to whether or not I was academically prepared to begin the MCAT prep course, and generally went the extra mile answering some questions specific to my situation. Sent me emails and data that I needed and spent about an hour on the phone with me.
When I called TPR, I couldn't help but feel like I was calling TimeLife Music and was about to hear that I would get an amazing set of Ginsu knives for only $19.99 additional. They didn't even take my contact info and whenever I asked a question, the answer sounded like it came from a canned 'script'.
Again, didn't really strike me as professional or individual attention, which made me think, how much are these guys going to put in to helping me achieve my potential?
In terms of content, they're probably about the same, just different formats. In Kaplan, you need to be motivated to dig it out for yourself (best way to learn, in my opinion) where TPR hands you a bunch of material and goes over everything (good if you learn from your classes, rather than outside work).
Again, YMMV and ultimately, the responsibility for this is yours, not a particular prep course.