Many students emailed and asked me if they should stick to one or if they should do both. I strongly advise all of my students to stick to one source of Qbank. And I recommend USMLE World Qbank only. The key to success is pretty much USMLE World. You should do USMLE World >2x to score high on your exams. However, many student starts to think that if they go over UW multiple times they can ace the exam. But in reality that's not how it is.
You have to know how to use USMLE World properly. And you need a good source to complement USMLE World. My recommended source is First Aid. Again don't just read First Aid like a newspaper. You should know how to use it with USMLE World. Lots of students don't know how to combine UW with FA, which perhaps is the reason their NBME score does not go up. If you are struggling with FA, do read my post on First Aid. And if you need any further assistance feel free to contact me.