Was wondering if any one has ever tested a Young carrier against a plain Jane carrier to see if there is an accuracy difference ?
Not everything in improving ARs is about accuracy. Young doesn't even claim better accuracy with their carrier, although I see how their description could be interpreted that way. The improvements they've made are really improvements to durability/life - more even and consistent bolt lockup leads to better bolt life, since load is shared better across all of the bolt lugs. More contact area on the sliding surfaces of the carrier should contribute to longer upper receiver life as well.
This fits in the same category as truing/lapping an upper - it's about making the system live longer. The fact that a lot of people misunderstand it and argue about the difference (or lack of) in accuracy doesn't change the true purpose for it.