I think NYC and New York City are essentially the same thing. In conversation and typing, I would much prefer to drop the FC out of either of them. Both work well I guess it would just depend on the context of what your talking about. When I followed the New England Revolution, nobody on the forums or in real life ever said New England, it became Revolution or Revs, depending on the context of the conversation. I think we should go that route, but with New York City or NYC. I don't mind just calling them City either, as I know who I am referring to.