Right now yes. They have the similar zoans fruit but Marco has regen to give him a boost, while King has swordsmanship. I give the edge to King. But if Marco was also a swordsman then King would lose his only advantage and would be a discount Marco since he could never outgun his regeneration.
He’s the only person who can die and it could make sense in story not only that he’s the only one who could die and for the banquet to still happen like usual because after this arc they are gonna throw the biggest banquet and for the first time since coming to the new world the straw hats will throw a banquet.
So yeah Marco is the only one who is going to die which seems fairly obvious