how is Nicks life in New York different from his life in the Midwest?

The Midwest represents a sense of honesty, hard work, and blue-collar practicality. These traits are juxtaposed with the frivolity, garish opulence, and corruption of East Egg. Nick comes to resent the values of East Egg and long for the Midwestern qualities that he had left behind:

That's my Middle West...a little solemn with the feel of those long winters, a little complacent from growing up in the Carraway house in a city where dwellings are still called through decades by a family's name..