Good question. A lot of students pondering which path to choose for medical school pose this same question. You will hear a lot of PBL students complain that they will not get everything they need for a "board" standpoint. While this can be an issue if you wait for people in your group to bring up topics, or try and tailor your cases towards board review, you shouldn't have to worry about it if you let the PBL system work for you and get the most out of the cases.
However, and not to sound like an arrogant ass, but this is the absolute wrong way to approach either curricular track. If you approach medical school as the beginning of a life long learning process, and you study like you may need that knowledge to save someone's life one day (and not pass boards) then you will do OK any way you choose.
Remember, even if you choose SBL, you still need to go to/listen to all the lectures, and you are still responsible for learning and committing that information to memory.
To sum it up, my best advise is to choose whichever path you feel will allow you to enter the clinical years the best prepared you can be (and only you can answer that question!)
By the way, my PBL class had a 97% pass rate and I myself scored in the 99th percentile on both step 1 and 2 COMLEX.
Hope this helps! message me if you have any more questions/concerns.