Concerning their moral character, both Biff and Happy have issues. Biff steals; Happy sleeps with his bosses' girlfriends, wives, or fiancees. The difference, though, lies in the guilt. Biff seems to feel true remorse for his misdeeds and a desire to change. He is willing to admit the truth about himself and his failings. Happy knows what he is doing is wrong, and even though he hates himself for it, he has no true desire to change.
As for their father and their dreams of success, Biff recognizes that his father is living a lie and tries to tell him. He tries repeatedly to let his father know that he himself has not and cannot live up to Willy's expectations of him. He will not be the financial success that Willy hoped he would be. Rather, he will go West where he can earn a modest living working outdoors. Biff also is aware that Willy has been unfaithful to Linda. His disappointment in his father derailed him for several years. Biff's words at the end of the play show his separation from Willy: "He had the wrong dreams. All, all wrong. . . .He never knew who he was . . .I know who I am, kid."
Happy placates, rather than confronts. He tells Willy what he wants to hear, but his connection to his father is much weaker than Biff's. He simply does not care as much about Willy as Biff does. However it is Happy who clings to Willy's dreams of success. He keeps working at what seems to be a dead end job, hoping that when one of his bosses dies, he will be promoted and finally get ahead. His chances seem slim. His last words in the play are "He fought it out here and this is where I'm gonna win it for him."