Oh man.... let me put on my analytics hat for this answer....
For physical sciences (in the TBR full lengths... as well as the passages), I would say that TBR evokes the same content that I've seen on the AAMCs. I've seen optics, I've seen solubility, I've seen pistons and work.... This is not to say that the AAMC ONLY tests on a specific set of content (that would be incredibly misleading). But, I feel that TBR is asking very fair questions. For instance, TBR will ask you what the speed of an incident electron must be in order to trigger the release of a photon; so will the AAMC. TBR will NOT ask you what the hyperflux angle of the dicationic quantum lever arm is (if they do... I would love to see the answer).
The thing that makes TBR challenging is that it prepares you for the worst case scenario on test day. And what would be the worst possible scenario on test day? To read your passages and have no freaking idea what the hell it means. So, TBR's strategy is to hit you hard on most (if not all) passages to FORCE you to focus, and to build out your powers of extracting useful data out of its ridiculous presentation. So, when you've answered 3,000+ questions in this style, you get used to a rugged road.
I remember the first AAMC I took after finishing...oh....2,500+ TBR questions. I got to a passage that, literally, had a diagram of a slope and asked for various velocities and forces due to friction. When you've been in the thick of TBR, you kind of look around and say, "W-wait.... this.... this is all they want? REALLY?... Wow. Ok!" So, while the AAMC isn't necessarily "easier", their passages are usually presented in a more palatable way.