In comparing both sets of literary elements in both autobiographies, I think we have to open with one glaring distinction: There is a vast difference in the narrative told by a slave vs. a free man in America. Without a doubt this reality tempers comparing the sets of literary elements in both autobiographies. I think that we can apply questions to better answer the literary elements with this distinction in mind:
1) How does the setting of each differ? How is the setting of each the same? How does the inclusion of slavery change the perceptions of each?
2) How does the issue of slavery change the characterizations of people outside of the main subjects in each work? For example, how does slavery alter the interactions of Douglass and how does its absence allow Franklin more opportunity in his interactions with others?
3) How does conflict change when the issue of slavery is included in the telling of both stories? Certainly, there is a dimension of social conflict that Douglass endures which Franklin does not.
In my mind, the comparison and contrasting of literary elements in both works is directly tied to the issue of slavery and its impact. I think this one issue changes both sets of literary elements quite drastically.