I like them both. In the Harry Potter movies, they often manage to get the creme of British acting to play the lead roles. Maggie Smith, Kenneth Branagh, and, as I was happy to see in the Prisoner of Azkaban, Robert Hardy and Emma Thompson. Harris was nominated for two Oscars and Sir Michael Gambon has won a CBE and, needless to say, been awarded a knighthood. The latter, I think, did an excellent job transforming himself for the role, though - I think that took a great deal of adaptability and talent. Harris, though, was an amazing Dumbledore himself. They both give a good name to British stageplay in all of their roles, however, and to pick a favorite would be a little bit tough.