Wow, tough question for my heart. Brandon is one of my all time favorites at UK. His work ethic, team-first attitude, clutch play, smarts, and scoring ability were dear to my heart. Having said that, he has GOT to get better at absorbing contact (avoids it too much), has GOT to work on his blow-by ablity (I think he has the ability, but hurt the team a bit when in the half-court and couldn't get by his guy, very easily).
Brandon will find a way and will not be denied, but it may take him a year longer than Kyrie, Kanter, etc. (I feel the same about Williams though, so take that for what it's worth.)
Kanter is a man among boys, from what I saw, and I would have NO fear of him being worthy of a top 3 pick.