It's about ability.
Andre Brown is faster, quicker, stronger a better receiver and more disciplined than Bradshaw.
Brown hits the hole quick and heads up field. He almost always even when nothing is there falls forward for 2-3 yards whereas Bradshaw would get no gain or lose yardage.
Bradshaw is not powerful on short yardage. Bradshaw was only used on short yardage in place of Jacobs because of his speed and ability to bounce the play outside. He can no longer bounce anything. he needs to be the backup.
Andre Brown's pass protection has gotten much better and he stays with the play rather than dance around and constantly try to go east and west(for all you Jacobs critics). Like I said if nothing is there he still gets + yardage.
Bradshaw would be good as a backup and in the second half when the defense is tired.