Are you doing any questions from a bank right now? I'm doing ~40/day on untimed tutor mode with completely random blocks. It's taking me like 3 hours to read all the explanations and annotate in First Aid. I'm not sure that I could double that in order to complete two banks before UWorld. We also have a full schedule right now so maybe that's why.
I'm doing Kaplan Qbank now and adding each question that I miss to the 'My Questions' list and once I finish the entire bank I'll start doing blocks from just 'My Questions' until I've finished all of those. Then I'll switch to UWorld and definitely get through it twice. I wanted to do USMLERx right now as well but I just don't know if I would have enough time to get through it. I basically divided the amount of questions in Qbank by the number of days I had to complete it (I want to be done by March 31). That gave me ~30 questions/day to complete in order to finish the bank in 75 days, but I'm doing a few more so that I'll leave myself a little room to go over my incorrects. I'm not sure that I could get through 60 questions/day and get the most out of it while still doing school.
I can't answer your question as to whether or not Kaplan is that much better than USMLERx, but I know that it has information in it that is nowhere to be found in First Aid. I like that. They definitely pile on the information in the explanations. I did a trial of USMLERx and it their explanations didn't seem as thorough, in my opinion. But that was only a trial. Maybe the majority of the questions in the bank have better explanations. I mainly went with Kaplan because I asked people on SDN, whom I trust, what they did and would do over again if they had to. A good bit of them told me to do Kaplan simply because it gives you extra info not in FA. That sold me right there.
I want to hear how you're doing the questions banks.