Heading into my exam in a week, my opinions on the various Qbanks...
Uworld is the best. It's not close. Uworld is by and far the single best board prep resource, surpassing First Aid, USMLE-RX, Pathoma, TrueLearn, AMBOSS, and every single other resource. If you had to choose one thing and lose everything else, I would pick Uworld every time. With that being said, Uworld is best saved for a time around dedicated when you've covered all of the material. Do not waste these questions.
USMLE-RX is a solid qbank and it's nice to be able to read directly into a specific First Aid page following every question. These questions tend to be more specific on details than other qbanks and, in my opinion, are written a little worse and has a fairly high incidence of "bad" questions. With that being said, it's a great resource to use before exams and to solidify material as you pass through the material given the attention to detail in USMLE-RX questions. This is probably the qbank I would recommend beginning after first year.
AMBOSS is a good resource, and I've used it primarily for its library in lieu of First Aid (it's much easier - like a medical Google). The questions, though, are generally significantly more difficult than Uworld, USMLE-RX, or TrueLearn and, in my opinion, not typically representative of your class exams or, I presume (from practices and the Free 120) Step 1. It is, however, like RX, very useful for hammering in small details. The function allowing you to select questions based on a specific library card is particularly useful in this regard.
TrueLearn is something I have through my school because it is akin to Uworld for COMLEX, but they also have a USMLE section as well. These questions are okay. I haven't touched it in some time and I will continue to not look at it until after Step 1, but if I remember correctly, the explanations are lackluster compared to the other available options.
