I shot .45 Long Colts in my Judge because it was fun. The more I shot it, the worse the accuracy became. I had to buy a special deleading kit just to get it all out.
The owner’s manual for my semi-auto shotgun advizes against using slugs due to leading. If I see a need for a single projectile, the AR15 comes out.
For self defense at close range the shotgun is always best simply because your aim will be off due to the excitement of a life threatening incident. With a shotgun it’s point and shoot with a reasonable expectation of stopping the assailant or getting him to run off.
Father-in-Law had a really nice 10ga. he would try to trick his friends with by putting a mag shell in as opposed to a standard 10ga. shell. That thing kicked like a damn mule and that’s NO exaggeration. Shot slugs out of it once; spent the better part of an hour looking for my shoulder back in the parking lot.