If Paul's knee is OK, then going from Billups, Melo, Amare to Paul, Melo, Chandler is a huge upgrade, in my opinion. Paul is one of the best pure PGs ever and makes everyone around him better. Amare is pure offense, no defense, while Chandler is mostly defense but certainly won't hurt you on the other side of the floor (I don't even think that you can say for sure that Amare > Chandler. The Mavs certainly don't win a championship last year without him. Everyone on that team agrees that he completely changed the culture there.). And Billups' best days are behind him, to put it kindly.
Although I have no idea why NO would prefer Amare to the package they were offered from LA and Houston. The NBA's killing of that deal was a massive embarrassment.