Rifled barrels work est with sabot slugs. Sabot slugs need the rifling to stabilize them
Smoth bore barrels work best with rifled slugs. They are weighted to be stable without rotating. The 'rifling' is just a crush point to allow in slight variations in barrels/chokes, its not really meant to impart spin on the slug.
Just to clarify regarding the Brenneke Black Magic slugs. They are design, and the package so states, that they can be used in both smooth and rifled barrels.
But best to check each ammo type for compatability. The general rule of thumb I've used is if you're shooting over 100 yards best to used a rifled barrel to get the added stability and lessen tumbling. Under a 100 yards a smooth bore is fine.