Doesn't really matter in my opinion. Both were tough. Whatever you do, if you get a poor score, keep your head up. I went from getting a 33 on AAMC 8 to a 27 on AAMC 11. The tests are hard, but they're great practice.
It depends. For me, AAMC 10 went great (and ended up identical to my real score) . I took 11 a couple days later and scored 3 points lower, so I felt kinda crappy going into the real test. However, the BS on 11 was a lot closer to the real thing than any other practice I did.