We can't actually answer either of these questions, because it all comes down to you and your playstyle. But assuming no bias either way, it's yes to both questions.
Slugs are pretty damn useful. It doesn't affect damage that much; people will still die before they have time to react; while drastically increasing your effective range. You can even out DPS certain rifles with a Slugged shotgun. I would almost always recommend going with Slugs.
