Dave McCracken makes it sound like different combinations of slug and barrel will yield different results.
Howard Brant raves about fully rifled Paradox barrels and sabot slugs ... although I can't quite make out what the expected accuracy is (article gets kind of vague toward the end).
One gent at Shooters' Forum says rifled tube groups at 125 yards compare to fully-rifled-barrel groups at 175.
On the whole, I'd say the rifled tube idea is more attractive to most shooters, since it gives you more options without buying and changing barrels. You could be enviably versatile in the field with a rifled tube, and IC tube, and a full choke, and a variety of ammo. The latter link above discusses on problem with rifled tubes - firing slugs through them causes them to tighten over time; you actually should keep loosening them as you shoot. I believe all of the above applies to sabot slugs. Combining rifled
slugs with a rifled
barrel is something I know little about.
On the pro-fully-rifled side, changing from slugs to shot often invites a change of sights. Some people like the rifled barrel idea since it gives you the option of mounting a scope on a cantilever; keep it sighted in and put it on for deer season, and switch to a vent-rib smoothbore barrel for duck season. So a question to keep in mind is, what sort of sights do I intend to use with slugs? A lot of slug accuracy is probably limited more by the unsuitability of the bead sight than by the weapon itself (someone who knows more can tell us what ranges the bead sight works for). A very interesting sight option, I think, is Marble's barrel mounted sights - aperture
or open sights.
okiewita40, what kind of slugs are you using? I gather that the Brenneke slugs can be very accurate ... not sure about Fosters. My guess is that the rifle sights were key to that kind of accuracy.
P.S. Here's a good book for terminology, whether or not you're hunting
whitetails.