[Mariner]

"For people who want the ability to get through furniture, walls or auto glass, slugs provide another option. "

00 or 000 buckshot works just fine for that application.

The only advantage a slug has over big buckshot is range and penetration of over 24 inches of muscle and bone.

[Mariner]

Or, if you ever have the inclination or need to shoot clear through a 10 inch diameter fir tree.

[ChildOfThe60s]

Serious recoil too.

Trying to shoot from the shoulder /aim it like a rifle with slugs is very hard on my neck.

I was told (accuracy undetermined) that #4 buckshot is the FBI choice over #00 because it still has good penetration and better odds of serious damage to vital organs.