The story is written in third person omniscient, and the author uses this style of narration to emphasize his theme. In the introduction, the narrator tells us how Rainsford loves to hunt, and he doesn't think the animals feel anything when they are being hunted. We get Rainsford's thoughts and feelings while he is being hunted by Zaroff to illustrate how it feels to be the hunted. Toward the end, the narrator breaks away and follows Zaroff back to his house, to his library, and then to his bedroom. I believe this shift in narrative is how the the author lets the reader know that Zaroff has now become the hunted. In this case, the third person point of view is used effectively as a tool to foreshadow the climax and the resolution of the story. This is one of the advantages of using third person. This is why an author usually chooses the style of narration for a story on purpose. Here, the author wants us to know that Rainsford is no longer the hunted, but he has now become the hunter. The roles have switched. Point of view isn't something that necessarily has advantages and disadvantages. It's a tool the author uses to make the story better and to serve a purpose in telling the story.