Uworld >> USMLE Rx > Kaplan >>> any other source of questions/question books. The Uworld surgery questions are good, but they're not the best distribution of questions (I think like ~50% are trauma/ortho). The other 2 banks are not as good as Uworld but have some different subjects and a different distribution. Don't delay going with Uworld, just do it and then go through the questions a 2nd and 3rd time. Do it at the same time as the other banks for the ultimate experience.