NJ has pieces, a LOT of good pieces, but I doubt they're ready to use up all of their assets just to land one guy. They've laid out one hell of a foundation... it may sound odd to say, but they don't really need Carmelo. In 4-5 years, if they stay their present course, they'll be looking really good anyways.
Charlotte on the other hand... They get Damp, they save a fortune instantly, get picks/prospects, and an all-star back. Hard to argue with that. Especially if they're trying to remain competitive while retooling their roster.