In an ideal world, you'd have time for both, but it's really not feasible time wise - hence why a lot of schools have dedicated board study time so that you can focus entirely on reviewing everything. The First Aid book covers about 90-95% of the material on the board exam. If you've had a chance to chat with some of the superstars that get scores in the 260+ range of Step 1, many of them will tell you that they basically memorized the book. For the rest of us that aren't superstars with photographic memories, we'd be doing pretty good if we could even absorb 80% of the book. Now if you had to not only commit First Aid to memory, but you also had to spend time to learn things not covered in it or time learning OMT or whatever else, your ability to cover First Aid must then go down.
I'm not saying the extra material is irrelevant to medicine. What I am saying is that it's really quite irrelevant for a 2nd year medical student to learn how to intubate someone or learn about specific state laws or some receptor that has no medical purpose. If the goal of an institution is to make good doctors, then it should be clear that the 2 most important things during the first 2 years of medical school is preparing them for their board exams and teaching them how to act like compassionate professionals. Why? Because these are the 2 things that will allow students to get a strong residency where REAL doctor training begins. If you have a 4.0 trying to learn all the minutiae, but your board score is a 200 on the USMLE, it's likely that your options for residency are going to be limited to weaker programs. I think it's unlikely that any student ever goes into medical school with the goal of being a bad doctor, but it's very much a fact that you can be caring and compassionate, but still be bad simply because your training during residency was subpar.