The Kaplan stuff is pretty dry and tends to take a kitchen-sink approach to the material, whereas the examkrackers has a much more interesting style, is in color, and is more concise. I would say that the examkrackers approach is much more high-yield in that you would have a harder time memorizing everything in the kaplan books than everything in the examkrackers books.
In any case, your motivation to work, quality of preparation via the pre-reqs, and brain power will be the overwhelming determinants of your actual MCAT performance. I agree with one of the other posters-- focus on one set of books and learn it thoroughly. They all cover the essential material, so trying to learn two sets of books will not help you in any way. It may even hurt you since you will have a less focused prep and may end up wasting time re-reading your strong concepts in two sets of books.