Compare Sonny in "Sonny's Blues" to the grandmother in "A Good Man is Hard to Find."
Although "Sonny's Blues" is narrated to us by Sonny's brother, Sonny is undoubtedly the most important character in this short story. He is something of a stereotype, as he is both a jazz musician and a heroin addict, and although the story begins with the brother's shame and anger that his brother has just been arrested for peddling heroin, as the story continues, we see that flashbacks are used to bring Sonny and his personality to life. When he decided he wanted to become a jazz musician, he worked at it seriously and studiously. When he was living with his sister-in-law's family whilst studying music, for example, they said that his dedication to music was so profound that "it wasn't like living with a person at all, it was like living with sound." It is only at the end of the story that the brother finally understands something of the massive appeal of jazz music to his brother as he hears him play in a club:
I seemed to hear with what burning he had made it his, and what burning we had yet to make it ours, how we could cease lamenting. Freedom lurked around us and I understood, at last, that he could help us to be free if we would listen, that he would never be free until we did.
Sonny and his brother move from conflict towards acceptance and love as the brother understands just how important music as a force was both to his brother and what it could do to help himself.
The grandmother in "A Good Man is Hard to Find," by contrast, is a character who is presented as selfish, vain and incredibly annoying. She shamefully manipulates her son, Bailey, and her family, getting him to go on holiday where she wants to go and she blatantly disobeys his pleas to leave her cat behind, indirectly causing the accident that leaves them so vulnerable to the Misfit. She is a character who, for all of her feigned "goodness" is actually exposed as a woman who lacks awareness. However, she, just like Sonny, in spite of her problems, seems to find something of grace at the end of the story, though not in music. When she reaches out to the Misfit and clutches at him, saying "Why, you're one of my babies. You're one of my own children!" she experiences something of an epiphany as she sees finally that she is just like the Misfit as a flawed human being.
The major similarity between these two characters therefore seems to be in the way that they face up to their various faults and foibles and accept themselves for who they are.