BWR13,
In answer to your question, as others have stated you will have better down range results with a fully rifled barrel. So now it comes down to a money issue and how far you plan on taking shots. If you are looking at taking longer shots, 100 to 125 yards, rifled is the way to go. But if all your shots are going to be well under 100 yards than the rifle choke or IC will work fine. I know some others have had great success with smooth bores out to 100 yards but the rifling is the way to go 100+ yards with confidence.
You will be able to use the sabot copper slugs through the rifled barrel and rifled choke. A sabot through a smooth bore will be very erratic. I prefer the copper sabot slugs through my rifled slug gun. If you use the IC a fosters or brenneke slug will probably work better.