I honestly don't see this.
King's durability (can Marco actually deal any lasting damage to him when even Zoro's mightiest attacks cannot), offence (consistently overpowering Zoro), mobility (he seems to have a speed advantage in his Hybrid form) and resilience/recovery/staying power(an Ancient Zoan) means that once he starts fighting seriously he wouldn't ever be on the back foot against Marco.
Marco's fruit will make it one hell of a slog, but as he did in canon, King will eventually exhaust his regeneration.
It's going to be a battle of attrition, and King will both be dealing more damage and receiving less damage than Marco. Considering that he's also an Ancient Zoan, this is not by any stretch of the imagination, a battle that Marco can hope to win.
I don't think King craps on Marco, but it seems as if he will win somewhat comfortably (little actual damage and mostly some stamina lost).
Yes you are right about it being a battle of attrition.
I think it is very much arguable that King's durability is an active ability [unlike Kaido's passive ability] since King directly blocked the Tatsumaki. Also looking at it along with the other instances where King was hurt/bleeding from Marco's attacks and Zoro's Onigiri.
I do think there's a solid argument that other Yonko Crews don't know the abilities and the workings of their competitors - the Calamities didn't know how Marco's fruit worked initially and they sustained damage.
This lack of knowledge will especially hurt against Marco, since he can essentially eat mortally injuring attacks and attack you when you think you've injured him - case in point his Bluebird attack on King in chapter 1006. It's fully due to King not expecting Marco to lose an arm/wing and still fight on like nothing happened, IMO.
The argument for Marco is that, he figured out what King was - a Lunarian - by the end of their encounter. I don't think he figured out King's ability and its workings though. But if both Marco and King start the fight with lack of knowledge about each other's abilities, there's a good chance that Marco will eventually figure out King's ability and its workings at some point during the fight, like Zoro's going to do.
In that case, it would be a fantastic battle of attrition with Marco looking to bypass King's ability and King trying to repeatedly attack Marco and exhaust his regeneration. I do think King would slog it out in the end, but it will not be a easy battle IMO.
You can also talk about their
near identical portrayal - Oda really went to great lengths to make King, the evil Marco.