I have humanities background and also had weak content knowledge and I went with TBR but also had Kaplan. Here's why I went with TBR and recommend it for most folks: practice passages that utilize spaced repetition to increase content retention and mastery. TBR is very detail oriented which helps with some of those nitty gritty discrete questions. Where Kaplan might cover a topic in one page, TBR usually will take 3 or 4. Some folks do not like that level of detail which is perfectly fine.
Regardless of which set you pick, make sure the *majority* of your prep time is dedicated to practice passages and not passive content review. I liked that TBR combined these two, before moving on to more dedicated passage practice with FL MCAT exams as well as practice passages from UWorld.
