Among other remarks, the critic Frank A. Littler refers to Faulkner's story as "a meditation on time...an allegory of the relations between North and South." So, without the narrators of "A Rose for Emily," much of this background on Emily would be missing. It is this history of the Grierson's and their house provided by the narrators that provides the contrast between the Old South and the New South with Emily as a relic of that former life.
Certainly, too, the chronology of the story would be altered if the narrative of the Faulkner's tale were told from first person point of view. With the "we" group narrating and recalling in a natural way, the Gothic effect of the ending is much more effective, for the discovery of Emily's grey hair is, indeed, shocking.
Then, too, there is the abnormal behavior of Emily that, viewed by the narrators, leaves out information that lends some mystery to the story, making it more intriguing to the reader and leaving much of the "work" to the reader.