I've been prepping with Kaplan for the past few months. I think Kaplan's style is great prep for the sciences. Its essentially the same content but more convoluted and logically confusing, but still for the most part follows the rules of science. This is helpful because the harder MCAT passages, even on AAMC materials, will be that complex and will require really being able to pierce through the veil of obscure biology terminology. The key to getting through them is not as much knowing what to read as much as it is knowing what to NOT read. That said, obviously closer to the exam you should be using AAMC materials.