In almost 48 yrs. of deer hunting with a shotgun and slugs I really haven't seen much difference in slugs.
I started out with a Win 1897 in 16 ga. and it shot everything OK for the 50 yds. I needed.
I always figured with a almost 3/4" hole I really didn't any expansion so never gave a thought on slug expanding performance.
Then I went to a Moss 500 with a smooth slug barrel and that's the most accurate shotgun I've ever seen and shot everythin just fine. My son still has it.
I now use a Rem 1100 12 ga. since 1980 with a smooth slug barrel and it shoots everything OK for 75 yds.
Remington slugs does give a slight edge but I buy whatever I can get on the cheap but always test and sight in the scope before hunting.
Now with the new PCR I'll use my Marlin 45-70 that shoots one hole groups at 50 yds. It'll do just fine out to 150 yds. I can reload my own rounds and won't have to depend on store bought shotguns slugs. Big improvement overall.