Welcome....
If you have the smooth bore stick with rifled slugs, first off they are way cheaper and are meant to be used with smoothbore. If your just deer hunting in MA, most spots you won't have over a 50-75 yard shot with the thickness of the woods anyway. I would stick with a more open choke when shooting slugs, like improved cylinder. They make several different types of fiberoptic sights that screw right on to the vent rib nowadays...try one of those. If your just using the gun for deer, I suggest a red dot type scope, those are very nice, quick on target, and good for shooting in low light.
If you do go for the rifled barrel, get one with the cantiliver scope mount on it, it makes putting a scope on easier and more accurate.
Sabot type slugs are meant for rifled barrels.....I really wouldn't bother switching barrels, unless you find shots are really far like over 100 yards, or your accuracy is really unacceptable, like you can't hold a group at 50 yards. If your shooting over 100 yards, you'll need a scope with some type of magnification on the gun anyway to make ethical shots.
