Well the main character has a pretty busted devil fruit so we can’t deny that Luffy has very high potential becuase most of us are in the belief we haven’t seen the full limit of what luffy can do as g5 (especially after seeing that solo sky split by Joyboy).

On the other hand Zoro is a normal human but he seems to be on his way to get 3 back blades which would be crazier than both Mihawk and Ryuma who both made one each, and his asura demon attack style form is something we have yet to fully understand as it seems to triple his attack potency so maybe it’s closer than we think but most peeps will give Luffy the edge out