Decidueye and Takumi are archers from Nintendo JRPGs that are some of the main cast of these hyped up 2016 games. Both can be a trusted ally or a deadly enemy to the protagonist that is mostly player determined and have a ghostly presence about them. Both are known for their skill as an archer and as a fighter and can also can have unlimited ammunition for their bow (Quills for Decidueye, Generated Arrows for Takumi). Both also work as a big part of a team to take down a creature from another dimension (Ultra Beasts for Decidueye, Vallites for Takumi).
I think Decidueye would win if this were to become a real episode. Decidueye would have helped fight more dangerous foes, has better speed in general, potentially greater destructive capabilities, and versatility. Not to mention Synthesis can be used to heal any real damage Takumi does to it. This would be a close fight, Takumi would not just hand Decidueye that win.