Both have rum, citrus and a sweetener, but a few differences between the two make for very different drinks and flavor profiles. Traditionally, a daiquiri uses white rum, simple syrup and lime juice while a rum sour uses dark rum and lemon juice. Simple syrup is also common in a sour, but you’ll see more variations of sweetener like you do here with the orgeat. A sour also typically includes the egg white topping, which a daiquiri does not.