Agreed. Your Physics prof is only going to be able to say that you got an A in his course in the letter. Someone can look at your transcript and gather that. Your organic prof will be able to say more about your character, work ethic, that sort of thing.Well if you were to only pick one, I would say go with the ORGO professor. He knows you better, its a harder course and he probably has a better idea of who you are (resulting in a better written LOR).