I would say that they aren't the "best" representation but great study tools none-the-less. Especially if you're getting them wrong and are learning from your mistakes which are great tools when setting the foundation of your content review. I found certain EK lecture sections harder than others in terms of difficulty, but that could be do to my own lack-of total knowledge on the topic. Always remember certain topics are more likely to be covered on an MCAT than others; so the more "common" topics may seem more genuine to the AAMC tests only because you may be seeing the same variety of questions MORE than others.