The sun shines in the daytime when it is light that is true. But it is only light BECAUSE the sun shines, if the sun did not shine then it would be dark (an example is when its cloudy it goes dark). Like when there is an eclipse and the sun is hidden, the world goes dark.
Therefore the sun is more useful, and anyways, the moon only shines because of the sun.
Shayar4ever, I'm a psychology student too, but in science i've always been taught that the moon only shines because of the sun thats why you sometimes only see half a moon, not always a full moon, so the first statement is extremly questionable.