These two characters work nicely for both comparison and contrast. They share many commonalities yet are also very different people in the play.
Beginning with similarities that connect Walter and Beneatha, we can look at the individual thrust that each maintains through the majority of the play.
Pressed by difficult circumstances into a rather desperate relationship with dignity, both Walter and Beneatha feel that they must do something to distinguish themselves and to attain a dignity and self-respect.
For Beneatha, this leads to dreams of becoming a doctor (at significant financial expense) and to thoughts of marrying Asagai (to adopt a Pan-African pride of identity).
For Walter, the need for dignity makes him want to quit his job as a chauffeur and open a liquor store; to take control of his financial destiny.
...he expresses his longing for a more independent life and a career beyond that of chauffeur for a white man...
Beneatha and Walter discover that pursuing dignity in these ways, while potentially successful, implies an individuation that separates them from their family identity. It is this family identity that finally unites brother and sister and the whole family (when they decide to move into the new house).
Looking at the differences between the two characters, we can see that they approach the idea of culture quite differently. Walter strives to succeed within his cultural paradigm, joining with friends to open yet another neighborhood liquor store. Beneatha takes the opposite approach, seeking ways out of and beyond the culture in which she was raised.
She rejects Murchison, the figure who courts her that best represents her own cultural background.
He claims to have no interest in African culture and is exactly the opposite of the idealist Joseph Asagai.
In her rejection of her culture, Beneatha comes into direct conflict with Mama, something that Walter avoids.