Here’s why King is probably the strongest Yc1 other than Benn Beckman:
He doesn’t have a gimmick.
In Katakuri’s case, the gimmick is FS. If an opponent can get past that, he’s not too much of a problem.
In Marco’s case, the gimmick is regen. If an opponent can get past that, he’s not too much of a problem.
King is (obviously) physically stronger than both, and he has fire abilities that (apparently) remind of Marco of Ace.
Basically, Katakuri is strong because of FS, Marco is strong because of regen, King is strong because he’s strong.