i would definitely go usmleworld. i did kaplan because i didn't know about the other until i had done about 1/3 of the questions. classmates said they saw some exact questions from doing world. i learn more from questions as well, and i definitely thought things were easier this time around compared to step one (not that i killed either one). i also noticed that kaplan didn't mix up things well- there were some subjects that i never saw until the last few sets of questions i did, and wouldn't have seen if i didn't complete the entire question bank. i think people in our school get a kickback from kaplan and they never mention any other options. world was half the price too, if i remember correctly.