There is a third scenario - that matches Benoit's issue, I think - where the share is configured to a path within a volume that is not a qtree - /vol/vol1/dir1/dir2, for example.
Benoit is correct in that snapmirror will only replicate volumes and qtrees, and will not work in this scenario - unless the option exists to snapmirror the entire volume containing the share, then delete what's not needed on the destination.
For this, ndmpcopy will work, with the caveats that I stated above. I've always used client side copies for this sort of thing, though - rsync or robocopy. These give the best solution when you need to minimize downtime, since you can do the baseline while the source is live, and only have to restrict access for the final sync and cutover.
As I said above, you would have to manually reconfigure the actual share.
Bill