The difference is that a lot more thought went into it. Not only that, the presidents domain of expertise and distinction/authority is about these issues. You way down your options, you navigate a complex issue with many factors involved. To prevent more death and suffering was indeed what was one of the most contributing factors of Roosevelts decisions (also to use it, as a direct assault on Japan would have cost a factor more in lives and suffering for both Japan the US)
The difference is of course a well thought out weighing of options, to feel into the issue and make your choice. Taking my immediate surroundings, a lot of people don’t engage in that level of philosophy. Knee jerk reactions are still very common in our species.
Using it was achieved by different kid level argument "It will prevent even more death and suffering"