The hunger felt by Richard is both literal and metaphorical. Taken literally the hunger felt by Richard signifies his family's poverty and deprived social condition. While staying with Granny in Ch. 4, for example, Richard writes the "once again" he knew hunger "biting hunger, hunger that made my body aimlessly restless, hunger that kept me on the edge, that made my temper flare ...". He then goes on to tell that every time he had a nickel he would go to the local grocery store and buy a box of vanilla wafers. He would eat them alone without sharing them with his family.
On a more metaphoric and symbolic level, Richard's hunger is to be understood as social and intellectual hunger. Towards the end of Black Boy (ch. 14), the portion that was originally published during Wright's lifetime, Richard says that whenever his environment had failed to "nourish" him, he had clung to books and these had evoked in him "vague glimpses of life's possibilities". Richard is hungry for the knowledge that the racist Southern society denies him so that he cannot improve his condition (see the episode where Richard forges a letter to the local library to overcome the ban on African American readers).
As for which of the titles is better, I would follow more recent trends in Wright's criticism in putting the two titles together. The two complete and complement each other and also evoke the publishing story of the book which was only published in the form Wright had intended in 1991. See also this interesting casebook edited by William L. Andrews and Douglas Taylor: