The best way to compare these three stories is to discuss the "effect" of each one and then describe how these effects are different. The stories have similar emotional effects upon the reader, but there are differences. "The Monkey's Paw" is uncanny and horrible. "The Tell-Tale Heart" is striking because of its insanity and wickedness, but the reader feels trapped inside the narrator's mind and shares his fear and dismay when his crime is exposed. "The Masque of the Red Death" is spectacular and allegorical. Its effect on the reader is more sad and sobering than horrifying. Your own emotional reactions to the three stories are what are important. Mine are only suggestions, and I'm sure they could be improved upon.