Part of the reason why Asagai could be a good man for Beneatha is because he would be able to embrace the changing identity within which she finds herself. Part of the reason why he would be more desirable for her than George is because he is able to embrace her need for self definition and personal identity. Beneatha's character is one that undergoes a great deal of soul searching and one where freedom is utilized in the hope and striving for self definition. Asagai seems like a man who would be more adroit with being able to help facilitate this exploration as opposed to stifling it. Having said all of this, it should be known that the characterization of Asagai is a complex one, as he does have a difficult time in allowing and affording total freedom for Beneatha in terms of where a women's emotions should lie. At some level, he does have some challenging in being to embrace the total conception of freedom that she represents. I think he is probably a much better bet than Murchison, but this does not strive to apotheosizes him in the process.
In the play "A Raisin in the Sun" Asagai is a man who is comfortable with his identity and heritage. He also likes to joke and have joy. Beneatha has trouble figuring out her own identity and she is very serious. He helps to lighten her moods and he helps her to figure out her identity.
Beneatha experiences frustration at the racism that continues to effect their lives. After the "Welcoming Committee" decides they want to try and buy out her mother before she moves into the neighborhood, she expresses that the life of a black person is like a continuous circle. It is Asagi who helps her to realize that their lives are moving forward in a straight line not in a circle. He helps her to know that things done today will have an effect on the future of others, but she would not be there to see the outcome. He is good for Beneatha because he helps her to stop her moaning and make plans for a future.