Generally tar to tar transfers have a couple more options, one being not to step across file systems, one being to keep symlinks intact (or not), and one being to avoid filling in 'holey' files.

Of course those things might not be true any more, basically I got habituated to using it when I was Sun and it continues to work, so my fingers haven't tried to learn a new pattern.

I think you mean cp -a. cp -R doesn't preserve permissions and other goodies of tar.