How is a branch nicer than a subdirectory? Off the top of my head, it seems like backporting bugfixes might be easier using a branch (if you're lucky, you can

How is a branch nicer than a subdirectory? Off the top of my head, it seems like backporting bugfixes might be easier using a branch (if you're lucky, you can just cherrypick the commit and it will work) - any other reasons?