As stated not all slugs are created equal, under ideal conditions any load that will kill a whitetail will certainly sort out a black bear. The PowerPoint hollow points are great for through the ribs but may fail if more penetration is needed. As stated the berneke style slugs are a better choice and the choice of the professionals I know.
I wouldn't hesitate to use a shotgun with slugs for bears and in a lot of situations would choose it over many deer rifles.
