Although they are set up as clear protagonist and antagonist -- Rainsford is the "white hat," General Zaroff is the "black hat" -- the two characters have more in common than differences. In fact, taking Rainsford's comment at the start of the story that the world is made up of "hunters and huntees" into account, it seems that he is only a few rationalizations away from adopting the same worldview that Zaroff has cultivated. At the end of the story, Rainsford chooses to return to the chateau and kill Zaroff rather than seek escape; this is often cited as proof that he has become the "new General."
However, they differ in one key point; Rainsford views animals as sub-human creatures, not deserving of excess cruelty, but also not of human sympathies. Zaroff views all the world as the same, with humans dominating because of their ability to reason; therefore, humans are as acceptable for hunting as any other animal, with their reason giving them an edge. Even during the hunt, Rainsford only sets traps when he is certain that he cannot escape through woodcraft; when his traps fail, he does not waste his life fighting the overwhelming odds and instead risks death to escape and live or die on his own terms.