Not sure where the idea came from that Foster style slugs are a poor choice. Foster style slugs tend to crush a human target. Having a "bullet" that expands to 1 1/2", and often fragments into 2-3 pieces, penetrates as well as your very best bonded JHP pistol ammo, and has a massive temp cavity (think 6-8" across) would explain why slugs work so well.
They work less well than slugs built for high penetration on targets like bears or cars, but they still work pretty good.