George Murchison is a pompous, wealthy black man, who attempts to assimilate himself into white America. He is portrayed as arrogant and materialistic in his valuing of image over substance. Despite George's professional success and education, he is a rather shallow man. He is more preoccupied with Beneatha's appearance, while Joseph genuinely cares about Beneatha's emotional state. George's elitist attitude also negatively affects his perception and reputation in the African American community. Throughout the play, Walter Lee Younger expresses his displeasure and contempt for George, and even Beneatha admits that he is difficult to be around. George views life as a competition and believes that wealth and social status equal success.

Joseph Asagai is a Nigerian student who studies in Chicago and courts Beneatha. Asagai values his African heritage and attempts to persuade Beneatha to get in touch with her African roots. He is a compassionate, intelligent, vibrant man who appears in a positive light throughout the play. He rejects American ideals and views men like George Murchison as assimilationists. His positive outlook on life and respect for traditional African cultures contrast greatly with George Murchison's perspective and his affinity for Western values. Although Beneatha favors Asagai over Murchison, she does not fully commit to him by the end of the play.

A Raisin in the Sun's characters of Asagai and Murchison are, as the previous posts noted, very different. The way they differ from each other makes them a kind of character that we call a "foil." A foil is a character that illuminates the important traits of another character by contrasting with them. 

Asagai appears to the ideal black man in terms of his ability to deal with being black in America. Ironically, he is not American, and that is probably what gives him his unique perspective. He still has a close connection with Africa and the identity it gives him.

Murchison, however, is trying to function as a black man in a white man's world. It leads him to feel scorn for others, such as Walter, who are struggling to establish their identity on their own terms, instead of trying to mirror white society.

Asagai is portrayed in a much more positive light. We see him as strong, independent, and wise. The female characters are drawn to him. Murchison is whiny and shallow. None of the family particularly care for him, even Beneatha, who is dating him. 

Hansberry uses the characters to examine two extremes in the black experience in America. It's obvious which one she values the most. The Youngers fall somewhere in between the two. By the end of the play, they have insisted on establishing their own identity on their own terms, even if it leads to trouble. They have moved in Asagai's direction. 

One of the most significant differences is how these two characters see themselves. George is an assimilationist. He acts white, embraces white values, and even dresses like a white man, down to his "faggotty white shoes." The theme of identity is central to the play, and George seems to be trying to reinvent himself as something he is not. He is ambitious, materialistic, and self-centered.

Asagai is proud of his heritage, but he doesn't make any particular effort to prove to others who he really is. And by the same token, he believes that service to others is a worthy, worthwhile thing, in contrast to George's materialism. Asagai is not afraid of being different; he would be one to embrace what we now call "diversity.