What do you see as the key differences between Biff and Happy?

In some ways Biff and Happy have reversed their roles in life once they leave high school. Biff had always been the popular "star" in high school while Happy lived in his shadow. However, because Biff does not actually graduate (mathematics was his downfall), he then is unable to get a good job. He begins to lose jobs because of his kleptomania and thus seems to be a failure. He is one side of Willy's personality, but he cannot quite abandon Willy's dreams and head west to do what he would like to do: work with his hands. Happy, on the other hand, has had more success after high school, but this success has come at the cost of having no moral compass at all. He thinks he is more important than he truly is, but has no ethics and notes that even though he has the "trappings of success," he is, in fact, lonely.