1.  "Intensification"

Although written nearly three decades apart, Mary Ladd Gavell's story "The Rotifer" and Gish Jen's "Birthmates" both focus on [common general theme or idea].  In [story A], [author] shows that [how the story treats the idea].  [Author B] goes further.  [Story B] demonstrates that [B's treatment of the idea, showing an intensification--a treatment more dramatic or consequential or final].

2.  Contrast Within a General Similarity (aka, "these two may seem similar, but they're really and importantly different")

Although written nearly three decades apart, Mary Ladd Gavell's story "The Rotifer" and Gish Jen's "Birthmates" both focus on [common general theme or idea].  In [story A], [author] shows that [how the story treats the idea].  However, [story B] demonstrates that [B's treatment of the idea, showing a meaningful difference--that is, a difference significant enough that the story's treatment of the theme actually amounts to a different idea]

3.  A contrast involving a formal "similarity" (ie, the various poems approach the formal element of setting differently, a focus on which reveals something important).

In Matthew Arnold’s lyric “Dover Beach,” the speaker experiences a crisis of faith.  Confronted with a ceaseless and seemingly meaningless natural and historical “ebb and flow,” he laments the inability of the “Sea of Faith” to provide any reassurance or security.  In this poem, the speaker seems powerless to imagine or render his setting in any other terms than those provided by the western literary tradition he invokes.  By contrast, Dorianne Laux’/Thom Gunn’s lyric  “______” offers a speaker who ______________ .  In this contemporary poem, the setting becomes _______________ .

[The example above would probably require another sentence suggesting what accounts for the difference—historical situation?  Culture or nationality?]