I mean, we're literally told that CoC is based entirely on how strong you are, and even if you consider Big Mom weaker than Shanks (a lot consider her stronger), it's not by a ridiculous amount, they're still relative.
Though Shanks clearly has more control and mastery over it, but in terms of potency, they should be close.
Though Shanks clearly has more control and mastery over it, but in terms of potency, they should be close.
My point is, them being relative in power does not mean that their Conquerors Haki are relative. Since Shanks clearly lacks the natural gifts & devil fruits of the other monsters, he should logically make up for it with better Conquerors/All 3 Hakis entirely & Swordsmanship.