Macbeth is enthralled with the possibility of the predictions coming true. He wants to hear more. He believes them; however, he is not satisfied with merely letting the predicted events play out. Rather, the predictions turn his mind to killing Duncan. Basically, Macbeth is drawn into their plot. While he says "chance may crown me, Without my stir," the thought of killing Duncan crosses his mind.
Banquo is much more leery of the witches. He asks them to predict his future and he seems to believe what they say. But he does not think that these witches have their best interests at heart. He says "oftentimes, to win us to our harm, the instruments of darkenss tell us truths, Win us with honest trifles to betray us In deepest consequence." He feels that the witches are up to no good.