Not sure of all the differences but they have different forks and the sm has a brembo stopper up front, the sm's are less common and if you find a good one it would be a great investment...matter of fact if you find a good one of both types youre doing well because most of them are ridden by the youngsters who thrash them everywhere, I bought one a while back (trail) and am so glad I did that
She'll be loaded up like a mule tomorrow, off to the aircooled RD rally in Derby, yes I know its not an RD :