It does depend on what lane you tend on going. Yasuo is trash toplane, so if your gonna be going top - Darius, Vice versa for Darius Mid.
When it comes to which is overall a impact in game? Yasuo no doubt. He's gonna carry. Darius goes as far as late game before he cant do anything else. If the ADC has a right mind, they can kite Darius to death.