I think your a victim of placebo additives, in that you THINK it is better , cause you paid more for it.
I have a friend who is a Shell development engineer. I asked him this very question,
he said " save your money"
unless you can watch the fuel come from the tank farm,( and know what your observing) there a very good chance
the fuel you get came from "who knows where!" local dealers DO NOT add anything, if they tell you they do, its to late for you, there is no hope!
watch the unmarked tankers fill from the tank farms, then deliver to almost EVERYONE!
I will admit some station monitor water content better then others, and that will make a big difference!