I'm not sure why you would not take the "harder" exams... Everything you have read on here would lead you to believe that the actual exam is much more difficult than the AAMCs.
By not taking the harder exams you're only exposing yourself to easier material and are just giving yourself a false sense of security. You should be looking for the hardest tests out there, that way there's no chance that you panic during test day once you see an extremely difficult passage.
It actually depends. Whether or not a test is harder or easier, is one thing, but what is more important is whether a test is
harder in the right way.
For instance, the later numbered Kaplan exams are not very good exams for practice in timed, full-length situations. They are very difficult, but that's not the reason they are bad timed-test preparation material. In my opinion, those exams are constructed in such a way that it may cause you think in a manner which is not conducive to answering AAMC type questions. They often convolute the logic, make you make inferences that are dangerous on the real exam, and often test on subject matter that is way out in left-field and has only been introduced in the passage. (The aamc has some interesting and sometimes bizzare passages, but everything is usually based on very basic principles.)
So in my opinion, it is more important to pick tests that require you to use a similar level and type of thought process that you will encounter on the real exam. What those are exactly I'm not totally sure. I found Kaplan 1-7 to be very useful, The TPR Exams up to about 4 are nice, and the Gold standard CBTs often have shorter passages, but they definitely try to trick you in the right way: a similar manner that the AAMC might try IMHO. You'll have to mix and match and see what works for you.
That's not to say that those harder Kaplan exams don't have any use, they just aren't that great for gauging your performance and improving your timed, pressure situation, test taking skills. They are really good for driving home difficult concepts and getting you to really understand the logic and science behind the material.
That being said, the real AAMC exams definitely are harder than the practice tests. IMHO, there is no question about it. Unfortunately, that means that there aren't many tests out there that are good preparation for "question-attack" and "question-timing" skills. Even still, I believe that the AAMC Practices are the best preparation we have.
