Without posting what kind of gun, what gauge, what barrel length or what kind of barrel I can't see this thread amounting to any kind of a scientific or factual summary.
THAT BEING SAID.
In my 12 gauge H&R USHs like Brenneke 3" Gold Mags and 2-3/4" Heavy Field Mags. They also shoot the Brenneke KOs pretty darn well too.
In my son's 20 gauge H&R USH he uses Brenneke 3" Mags.
I also have an old 12 gauge JC Higgins pump with an 18-1/2" smooth bore barrel that likes the old 2-3/4" Brenneke Rottweillers with the felt wad screwed on the back but my stock is low and they are tough to find. I don't even know if they make them anymore. So lately it has been shooting 2-3/4" KOs.
Then there is a Mossy 500 with a Remington cantilever rifled barrel. I think it is 24". It will shoot the 2-3/4" KOs pretty well but shines a bit better with the Remington Buckhammers.
In my experience I would practice with BUT NEVER EVER HUNT WITH Remington Sluggers. Too many brass and primer issues. IMO not reliable.