"The Raven" is a poem, of course, while "The Pit and the Pendulum" is a short story. There is a bit of a narrative in "The Raven," though. We know Lenore is dead and that the narrator is grieving, but we don't know much more than that. The real "story" in the poem is the emotional disintegration of the speaker. Poe takes us through the many stages of his grief; the narrator is on an emotional roller coaster that ends in complete despair and hopelessness.
"The Pit and the Pendulum," in the form of a short story, also traces the emotional turmoil of a narrator, but the tone is different. "The Raven" is mysterious and sad; the tone of "The Pit and the Pendulum" is one of horror, as Poe intended. Of the two, I enjoy "The Raven" more because of its mysterious, supernatural elements.