I can't say what the best slugger out there is but I can tell you what I use; I started out with a barrel combo for Win 120 Ranger(pump) which I bought in 1990, it was a smoothbore 24" rifle sighted open choked slug barrel. Pretty accurate with Win rifled slugs out to 75yds and took 4 deer I then upgraded to a Win. 1300 deer barrel with screw in chokes and installed a Carlson rifled choke tube which shrank my 75 yard groups using the same Winchester 1 oz rifled slugs, I now use a Mossberg 500 20ga with fully rifled ported barrel and has a cantilever (integral base) scope mount. I use a Bushnell Banner Dusk to Dawn 1.5-4.5x32 scope.
My loads are; Win. BRI sabot slugs, Rem. All Copper sabot slug and my cast Lyman sabot slugs.
This is very accurate compared to my smooth/RCT barrel from 25-125 yards. I gain an extra 75 yards using the fully rifled barrel.
This shotgun is new to me this year so I haven't taken any game yet. My next slugger will be a "Fully Rifled" barrel for my Thompson Center Encore in 12ga,
Cheers,