Similarities: They are both rather horrific; one tale is about a woman who murders her love interest and sleeps next to his rotting corpse, and the other is about a family and grandmother brutally murdered in cold blood. So, they have that horrific element, a "shock" factor, especially in the endings. They are also both insights into families in the old south, and the older class system of wealth and nobility. Both the grandmother and the family that Emily came from have very strict notions about the "upper class" society, and what is decent behavior. They are both rather snobbish, prejudiced, and hold to outdated customs that are not current in today's changing times. Another similarity in the stories is the unknown factor that changes everything. In "A Rose for Emily" it is Homer Barron; for the first time, Emily has a love interest that she is free to choose. The second they start being seen together, things change. She flies in the face of tradition, and then in the face of decency and morality as she is about to lose him. In "A Good Man is Hard to Find" things change when the Misfit and his gang come onto the scene. All of a sudden all of the beliefs and prejudices of the grandmother don't matter anymore; she is up against a force that will change things irrevocably.
Contrasts: In Emily's situation, only one man's life is taken, in the grandmother's her entire family is wiped out. Emily is the "murderer" in one, in a subtle and psychologically understandable way; the Misfit is an out-right, merciless and senseless killer. The settings differ; Emily's story is all in one house, and the grandmother's span a state, and end in a foreign place to her. At the end of O' Connor's story there is a message of redemption as the grandmother has a vision of sorts before she dies, where she realizes that we are all connected, equal, and loved in God's eyes. But there is no message of redemption in Emily's tale; just pity, repugnance, and distaste for the situation.
Those are just a few ideas to get you started; if you mention them, along with some ideas of your own, and use quotes from the stories to back them up, I think that you should be able to whip out 5 pages no problem! Good luck!