In fallout being the bad/good guy is all about short-term vs long-term benefits.

Evil - Kill everyone, get their guns, their bullets, their armor.

Good - Politically resolve situations. Often less/equal money. Requires more diplomatic skills. Potentially less ammo, less guns, less armor. However you can rob everyone blind and still play the good role :)

Its all about creating allies or trade routes or killing the hell out of everyone.