Most people I've spoken to claim that TPR Full Length exams are much harder than the actual exam. TPR exams are very content heavy, math heavy, etc. They focus on concepts that you might not expect to see as often/as detailed on the real exam.
It's excellent training to prepare you to move towards taking AAMC based passages but if yo're just starting your study path then focus on learning the material, take TPR full lengths to test your knowledge and test taking ability. Your score will increase, just keep at it.
The C/P - TPR is much more detailed
The CARS - Personally I've found it to be at level with the difficult of AAMC cars
The B/B - TPR is all about memorizing bio info, but AAMC you need to analyze passages and understand experiments - they differ a fair bit IMO.
The P/S - AAMC focuses a bit more on neuro than TPR does, but again AAMC has more experiment based questions - still a lot of memorization in this section though
