Surprised to see this on HNs front page when there's an Oscar-winning documentary that makes this pretty clear (Errol Morris's "The Fog of War"). Vonnegut also talks about this on Slaughterhouse-V: "The advocates of nuclear disarmament seem to believe that, if they could achieve their aim, war would become tolerable and decent. They would do well to read this book and ponder the fate of Dresden, where 135,000 people…
He's more right about the Tokyo bombing. Richard Rhodes, in his fantastic "The Making of the Atomic Bomb", cites 100,000 dead and 1 million injured.
[1] http://en.wikipedia.org/wiki/Bombing_of_Dresden_in_World_War...
[2] http://www.dresden.de/media/pdf/infoblaetter/Historikerkommi...