They are all small people who are bullied and insulted and have no ability to fight back. They are victims of social injustice.
I'm not sure what the difference is.
It seems that one is poor and the other is nobody, because of his low rank.
Bashmahin's image seems to be richer. He died because that coat changed his attitude towards life, because he realized that living in such a society was meaningless. It is not a good thing when a small person begins to find himself redundant.
Nicholas Nikolai Gogol killed his hero, because only in this way can he keep a little dignity of the awakened hero.