I have Smarty on my commuter or Candy on my mountain bike. Not sure if it is real or perceived but I find the Smarty easier to disengage. Otherwise I find them to be exactly the same. DH bent a Smarty spindle, not sure if it is not as strong but it seems a little lighter weight than my Candy spindle.

Rails are pop on plastic colored things. Just for looks and customizing your smarty pedals.