Hiroshima and the First Weapon of Mass Destruction

I just finished watching the Discovery channel show about the first use of Atomic weapons. I am always interested that the numbers of casualties are promoted to show the immoral use of the weapons that ended WWII. It seems to be only rarely mentioned that more people died in the firebombings of Tokyo or for that matter Dresdem.
I supposed the reason why atomic weapons are considered so horriffic is that their effects are accomplished by only one plane and one bomb. Makes it easy to form the mental picture I suppose, than trying to imagine 1000 B-29s at the same time. But, are the causalties of Hiroshima and Nagasaki really due more consideration im memoriam than the victims of the Tokyo raids which were done by a 1000 plane raid?
I did learn something interesting, that the Japanese military considered their use to not be as significant as the civilian leadership.
Maybe, it's because nuclear weapons are really political weapons, with very little real military value. Generally speaking, military use of nukes is only justifiable as a last resort; because you were unable to stop your enemy in a conventional maner.
It probably doesn't fit into our cultural image (Think Dr. Strangelove) that the military is hot to use the weapons given to them. Although I think that they would if ordered, I would be surprised if they thought it would accomplish much.