Both poems tell of a male speaker's longing for a woman, but their tone could not be more different. The speaker of Poe's "The Raven" is morose and melancholy; he is thinking of Lenore, his dead love, when a raven flies in. He masochistically questions the bird, each time receiving the same answer: "Nevermore", which he takes to mean that he will never again see Lenore. His insistent questioning is seen as sign of mental instability, since he knows the bird cannot give him a true answer, and yet persists in his questions.
Yeats's poem, on the other hand, tells of a fleeting vision of a woman, perhaps a faery. The speaker then begins his wandering in search for her. Though the poem is also melancholic, it is a lighter sort of melancholy. Though we may surmise that the speaker shall never find her, he himself has not lost hope and his wanderings seem less gloomy than the dreariness of Poe's poem. His goal (kiss her lips and take her hands) has a sensuality that dispels any sense of doom.