See I thought that the Kaplan tests were almost identical to AAMC material. When I was taking the actual MCAT, everything on it made me feel like i was taking another Kaplan Full length....same font, same format, VERY similar questions, and overall same difficulty (Kaplans always seemed a little harder, but this doesn't really have much to do with what score you are getting)
This is only my opinion, but from what I hear from most people, they agree that Kaplan tests are a little more difficult than AAMC practice tests and the real MCAT.
It's always just good to take the most recently crafted tests, because I feel like some of those early AAMC tests were just too easy and not really reflective of the current tests.