Do you do the lecture tests cold (lectures only) or do you complement the lectures with practice problems ? I find this especially true for physics, but hey- that's just how I learn good.
Personally, I used the entire EK set. Takin' the lecture exams after plowing through the lectures were a hit or miss- easy or hard. Complementing them with practice problems while going through the lectures helped tie the concepts to applications. Plus it helped me remember the formulas and problem-solving process mo' better.
But then, it really is ALL about the MCATs. (God! She is such a dramaqueen.)
So whatever helps you learn best.