Shanks has most likely better CoC than Rayleigh. Shanks was from the very beginning portrayed as a CoC monster and an incredibly ambitious man, with CoC being a reflection of exactly that. While Rayleigh followed Roger's lead, Shanks became his own captain of a powerful crew, which was highlighted by the Marines themselves as being a crew of powerful individuals, falling to Shanks' command. With Shanks' influence and accomplishments being truly astonishing. Clashing with a WB on meds who still had his sky splitter CoC, fighting off Kaido, commanding the Marines to give up, end the war and hand over Ace' and WB's bodies, as he will not allow them to be humiliated and with the fleet admiral followimg command. He even walked into the holy land, not being associated with the Gorosei (hence they asked what he wants and that he shouldn't be here), yet the Gorosei letting him speak "since it's him".