PS: like everyone said, Kaplan has more calculations whereas the AAMC/ real MCAT have very little calculations. AAMC test are more like," if we where to increase the distance between the plates of a capacitor, would the capacitance increase by 2X,4X or decrease by 2X,4X. It's more about the relationships when it comes to the real MCAT. They test on the concepts more heavily. Make sure you know Ksp and solubility for the MCAT.
VR: I felt that the real MCAT was more ambiguous than Kaplan's VR. The VR section of Kaplan's FL were more specific whereas AAMC's are more touchy feely. You'll never feel good after doing a AAMC test cause you're never sure of any answers. In Kaplan's VR, there are more questions where you are sure the answers are right.
BS: They are pretty comparable.
Overall: I think Kaplan's test are pretty good indicators of how you'll do on test day. I was averaging between 25-29 on my practice test and got a 28 on the real MCAT. Everyone that *I* know also got within a few pts of the practice test.