The Dalai Lama's argument starts from diffferent premises. If tourists do go to Tibet, then his people know they are not forgotten by the outside world, not locked in a madhouse with the key thrown away, and they can communicate their suffering. Our presence keeps them sane, and gives them hope.
Not long ago I faced the dilemma over both countries, and the Dalai Lama's argument won for me. It is doubtless better - if possible - not to travel on a package, when one's money really does go direct to the authorities. If there are no foreigners to bear witness, oppressive regimes can perpetrate anything upon their people and get away with it. That our awareness of Burma's chain gangs comes from a tourist's camera proves the point: without going, there is no knowing - and no telling either.