At their prime, Master Army is organize and a force to be reckon with. Many years later, those who understand that the army is done, they are all but retired but manage to integrated into society quite well, though racism still exist.
The East Coast Super Mutants are just mindless brutes to serve as something to kill.
What about Fawkes and Unlce Leo
I always see them as "because they are not evil like the resident Super Mutant, that mean they are awesome and strong!" mentality. In a way, I don't like it.