I have owned and tried out so many slug guns it is not even funny. I have had the H&R 20 and 12 gauge ultra slugger's, Savage 210F bolt action, Remington 870 with a Hastings barrel, Remington 1100, Remington 11-78 Slug gun, Beretta Xtrema slug gun, and a Encore Slug gun and I am sure a few others.
My most accurate slug gun, and I hated that I got rid of it was my Remington 1100 with 2 3/4 inch Remington copper solids.
I replace it with my Beretta Xtrema slug gun, although not quit as accurate, but close with Light fields 2 3/4 inch 1 1/4 oz slugs. I still have my Remington 870 with the Hastings rifled barrel, and it is a great shooting gun with the Light fields 2 3/4 inch 1 1/4 oz slugs. And now my Encore is another fine shooting rifled slug gun with the Light fields 2 3/4 inch 1 1/4 oz slugs.
So for me, the best slug gun for the money is the Remington 870.