Buck shot out of a rifled barrel will pattern horribly. That is, you will have a hard time hitting anything with it.
I'd try the cylinder bore with rifle sights (or ghost ring) and see if it won't do what you want.
With practice from an 18' or 20" barrel, you should be able to keep them in a 10" plate at 100 yards. (And not a lot of practice at that.)
During the training I have seen, the cylinder bore is most versatile and will serve your needs of both worlds.