I've shot a buck with a smoothbore/rifled slugs (my first buck) - and when we were restricted to shotguns, I've also shot with a rifled barrell and a good 3-9x50 scope on a slug gun at distances I'd never be able to touch with a smooth-bore.
Ultimately, It comes down to where you're hunting (in the woods?) and your budget - but my personal opinion is to always buy the best you can afford for the situation you need it for.