Chris Paul had fewer years left on his deal and Eric Gordon had shown more in his career at the time he was traded than either Noel or Smart have to this point. For a comparison, you know how James Harden is widely viewed as the best young shooting guard in the game? Eric Gordon was widely viewed as being right on the cusp of becoming just that when he was traded.
The Melo trade is a bad comparison since the Knicks gave up three prospects, a solid veteran (at the time) in Felton, and several draft picks for a guy who was going to be a free agent in four months time at the very most. Giving up two prospects, an unproven rookie, and middling draft picks for a solid big who's under contract on one of the best deals in the league for another three years? That's a great deal.