You're kidding yourself if you really think either of them fought on the same level as WB even when he was dying of disease and battle wounds he was still above them. People give the admirals too much credit based off of hype, Akainu beat Ace so everyone acts like he's this God. Ace sacrificed himself on that kill punch and they held their own in the war they didn't really take out any of the big guns though.
As for his Haki it is as strong as Luffy's hence when they fought each other and both hit with Haki they made the air around them
crackle from the force. Now this isn't my only source of info but it's the easiest to showcase my point
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Here in the Abilities and Powers section it says "He can also use Busoshoku Haki to harden his fist to augment the force of his punch, which turns shiny black, and clash evenly with Luffy's respective usage; the strikes resulted in the air itself crackling" as well as "Upon Luffy's strike restoring Chinjao's head to its old, pointed shape, his legendary strength from thirty years ago was restored, enabling him to split the Corrida Colosseum's arena simply by falling onto it head first"
Chinjao is back to his 30 year prior self which had to be beaten by Garp. You think the Marines just happened to send Garp after him back then? They could have sent admirals to handle him but they obviously weren't strong enough then and Garp is still stronger than admirals today so why do you expect Chnjao wouldn't be?