It’s not that Bobby is necessarily the worst option out there. He has a very bad track record with little guys so far in every story I’ve written him in (beginning with his original canon appearance in Bowman of Wellwood). The guy thinks that being bigger = being in charge. Combine that with seeing his normally 6′5″ friend at such a small size, and there would be a lot of teasing. He’d most likely be a bit too harsh for such a little guy before he stopped to listen.
Sam, being the independent and confident little guy that he is, would probably annoy Bobby a bit (Why isn’t he acting at least a little intimidated???). They’d need Jacob there to keep him focused.