All tests besides AAMC tests tend to be more difficult than the actual test, and they test information that you really don't see on the MCAT. I've never used to EK tests, but I did use their books which seemed to be really focused on MCAT material. I used all AAMC practice tests, scored in the 32-35 range on them and then scored 38 on the real thing. My recommendation would be AAMC tests for sure.