Willy Loman and Cora's biggest difference is their definition of success. Willy is trying to achieve economic and popularity success. He measures his accomplishments by how much money he has made and by the amount of people who "know" him. Cora Tucker's ultimate success is to create a equal opportunity for all people within her community. She could care less whether people like her or not, that isn't her goal at all. Cora is working to enhance the lives of others while Willy is only attempting to better his own family.
Their approach to achieving these goals also differs. Cora consistently works against the system, finding flaws as an outsider and "raising hell" about them to the people who control the inside. She isn't trying to make friends or become well liked, she is there solely because she knows the system that is standing now, isn't consistent to everyone. Willy on the other hand makes him self likable. Society has morphed him into a shallow person, who disregards actual talent and skill and disguises it with a fake facade. He knew his son Biff was never going to be the "smart kid" but his Willy was proud that he was the popular kid and thought that by being well liked Biff would automatically reach success.
The idea or accomplishing these life aspirations from Cora's perspective is attainable, yet Willy will never reach a feeling of ultimate content because his success is defined by the world around him which is constantly changing.