One of the smartest Engineers I know said it best:
His mentor (at the time they still mentored) took him aside and he had him watch as he signed a project out. He said, he is responcible for every part of this project. By signing this if anybody gets hurt it was his direct fault. If anybody dies, he committed murder.
He said everytime he signs a paper, it is all on him, because he engineered it.
Taking a direct responcibility, taking the time to check every detail, again and again. It is infurating sometimes to work with some of the best engineers, because they check every detail, and over build. But they feel personally responcible.
I think that is the difference. That checking, double checking, to make sure they are correct. Living with facts and calculations, but also making sure they have covered every best option.