As far as I can tell, XZ is a container that uses the LZMA2 algorithm (i.e. extended LZMA); but e.g.
$ xz foo/
foo/ being a directory. So presumably the correct way to preserve directories with XZ is with
tar; then what is the difference between
tar --lzma and
(Note that I do explicitly want ownership and permissions preserved, which is why I'm not just using 7z.)