All the AAMC tests, 1-10 are great practice since they were once actual medical college admission tests. And the difficulty and type of questions really hasn't changed a great deal, just the # of questions. So you will get a good idea of how the mcat-makers think.
The older, paper ones are longer, but taking the MCAT (even today) is a marathon. So if you take longer ones, you will have more stamina/concentration for the real thing and the later 8,9, and 10 practice tests. Those are the tests you should really focus on.
8, 9, and 10 AAMC tests should be taken near the end of your studying since they are the most reflective and accurate. Don't waste them early on since they are the closest in resemblence and will relax you on the real test day.
Don't bother with test prep company tests. Why would you? Taking 10 full-length AAMC practice tests is plenty. I didn't even take all ten, even though I wanted to, because there were just too many! I took like 7 or 8 of them.
Good luck.