One key difference is that Macbeth is the more obviously evil figure. He makes a bad choice early in the play and then keeps "doubling down" on that choice throughout the work. In contrast, Othello makes a crucial mistake late in the play, and for all kinds of reasons his evil does not affect nearly as many people as Macbeth's does. Othello is far more a victim than Macbeth is.
One difference is in what it is that leads to their downfall. Macbeth is driven to his downfall by his excessive ambition -- he wants so badly to be king. By contrast, Othello's downfall is caused by his jealousy -- he is very jealous with regard to his wife.