Apa perbedaan antara `su -` dan` su --login`?

Entri manual Debian tampaknya lebih mencerahkan:

   -, -l, --login
       Provide an environment similar to what the user would expect had the user logged
       in directly.

       When - is used, it must be specified before any username. For portability it is
       recommended to use it as last option, before any username. The other forms (-l
       and --login) do not have this restriction.