Dugtrio is the fastest SR setter and can trap Magic Bounce users for a guaranteed SR, while Mamo is immune to Taunt and thus isn't as vulnerable to faster taunters like Prankster Sableye or Weavile. Overall, I'd go with Duggy almost always. Trapping allows a smooth switch into Cinderace on a mon that usually doesn't have Taunt so u can gurantee the Court Change. Mamo can set up on Weavile sure but when you switch into Cinderace then you're just getting taunted anyways.Would Dugtrio or Mamoswine be the better Stealth Rock setter in a non-NatDex Court Change team? I believe they're the two best SR setters in the non-NatDex meta because Dugtrio is the fastest and has Arena Trap, while Mamoswine is the fastest setter with Oblivious (and is neutral to SR, while Dugtrio resists). Mamoswine scouts for anti-Court Change tactics more poorly, though.
Below is a list of sets with descriptions on how to use a good majority of viable mons currently found: