Another possible compare/contrast might be "Death of the Hired Man." This is also a narrative poem, also set in rural New England, a story about taking in a dying man who was not a satisfactory hired man on a farm. The poem includes this famous line:
Home is where, when you have to go there, they have to take you in (122-23).
This idea makes for an interesting contrast to the idea that fences make good neighbors, since it concerns itself with taking someone in, rather than keeping someone out. Do barriers make a home, or does a lack of barriers make a home sometimes? What are our obligations as good neighbors? Do we need community or do we need solitude?
The attitude of the wife in the second poem might be contrasted with the attitude of the narrator in "Mending Wall," while the attitude of the narrator in "Mending Wall" might be compared with the husband in the second poem.
If I were writing such a paper I would choose Frost's famous poem "The Road Not Taken." In that poem he had to make a career choice. We know he chose to live a simple, austere life as a New England subsistence farmer in order to be free to devote much of his time and thought to his creative writing. So then "Mending Wall" illustrates the result of that choice. It shows him doing hard manual farm labor, and it also shows how he makes poetry out of the life he chose for himself. It is almost as if his poetry grew out of the soil he was tending. The compare/contrast paper would throw light on both poems. They are similar in that they both relate to his choice of a lifestyle. They are different in that he is traveling in the one poem and is rooted to the soil in the other one. In one we see him making his choice; in the other we see the result of that choice. Both are autobiographical--and I would call the speakers in both poems by the name of Robert Frost rather than calling them "the speakers." Frost made it abundantly clear in public appearances that he was writing about himself. Frost emphasized that anything written has to be dramatic in order to be any good. So I would mention how he uses conflict to make these two poems dramatic. In one it is an inner conflict; in "Mending Wall" it is a conflict with his neighbor.