How representative is Khan academy vs AAMC question packs?

I've been studying for the MCAT in May and I'm about to start taking AAMC practice tests. Up to this point, however, I've been doing review with EK, Khan academy, and the AAMC practice materials. I've found that the Khan academy chapter questions are challenging, while the AAMC question packs have been almost comically easy. Both were developed by the AAMC, so I'm surprised by how different they seem. Has anyone else noticed this trend? For those who used both, which seemed more... How representative is Khan academy vs AAMC question packs?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums