If we are talking about best player it is McDavid. If we are talking about most impactful its Giovinco, as a striker in MLS, he has more input over TFC's on field success compared to McDavid. Giovinco plays in a much larger percentage per game, and has a larger impact on TFC's scoring per game than McDavid does. In all honesty it has more to do with how soccer is played compared to hockey than anything.