While I love Kaplan Qbank, I have not done its practice exams. Is it updated to the current exam (ie. 40 questions, 8 blocks?) How are the explanations? If they are similar quality as their Qbank explanations, I would highly recommend doing it for learning purposes if you have time.
Highly highly recommend UWorld Self-assessment. Most of the time, it predicts the actual score closer than any other practice exams.