Caliban is more of a menial servant, performing physical work for Prospero. On the other hand, Ariel is concerned mostly with magic, and is more detached from earthly things. Caliban is also more unhappy with his servitude. He is more "human" in the sense that he has worse thoughts and more dreams. He wants to be free, and is willing to commit immoral acts in order to achieve it. Ariel, who is more highly valued by Prospero, finds servitude more tolerable.
