Let's start with a comparison of roles. Both narrators are there to help the reader understand the natural flow of the story, and to provide clarification where necessary. In addition, both narrators are seemingly omniscient, meaning that they know everything that is happening or will happen. Judging strictly by tone and word choice, it would seem that both narrators are male. Such a choice was prevalent during the eras that both stories were written. If a story was to be told, authors largely chose a male voice to relate it. Twain was particularly fond of the front-porch-storytelling-grandpa-style narrator in his stories. His audience could identify with such a practice during the time-frame in which he wrote. Irving, however, chose to be a bit more neutral, simply telling the story in the standard "voice" of the times. Several other contrasts can be made, as well, if the information is required: Rustic vs. Formal, American South vs. New England, etc. Hope this helps.