I don't think anybody should be surprised by whatever BB decides. Mac has more experience in the system, has shown he can win, and hasn't reached his ceiling yet. BZ has looked really good in his brief tenure, has shown he can win, and hasn't reached his ceiling yet. Where they were drafted is a non-factor. Salary and tradeability are small factors that I doubt BB will consider; he'll want to keep both.
One interesting factor is how BB will weigh the present versus the near future and longer future -- i.e., who's better positioned to win right now, this season, and in future seasons.