Each test has some sections that are harder and some that are easier. You can find the score conversion charts for each of the AAMC on some old SDN threads. Generally, the more lenient the score conversion chart is for a section, the easier the section is.
For example the scoring scales tell me that:
Test 3 has a pretty straightforward PS and BS, and an average VR.
Test 6 has a hard BS, an average VR and a somewhat challenging PS.