I've found slug guns to be like rifles: they all seem to have a 'preference' for different makes/models of slugs. You said you use 'Remington' slugs....Remington makes several different models of slugs: buckhammer, foster, copper solids, ect.
I would suggest sticking with foster-type slugs, esp. since you wish to use them in your full choke barrel (however, if it was me, I would use it in the modified....I prefer adjusting elevation rather than windage). Winchester, federal, and Remington all make a foster type slug. In my firearms, Brenneke are consistantly accurate out of all my guns, with Remington a close second (these are slug barrels with rifle sights, mind you). Winchester slugs are accurate out of a couple of my guns, and Federals just don't perform worth crap out of any of my guns! I'd suggest buying a box or two of each and see what they do......kind of expensive, but you'll then have your answer.
