So it looks like the proposed Gasol trade would come down to Deng/Gordon, Brown for salary purposes and our 07 first round pick. Baring discussions about whether it would be better to swap Hinrich or Noc since it looks like the Grizzles want Deng or Gordon, which one is the better trade for the Bulls? To me there are two criteria to consider: salary implications and rotation implications.
From a salary standpoint, which of the two is going to ask for more money in an extension this summer? Does Gordon think he is worth max money? Does Deng? Paxson might have had some leverage with both sticking around and using the argument that the Bulls need both to be effective and that taking a home town discount ensures both that they will be playing with each other. Assuming they get along well, and I have no evidence to dispute that, it seems like a plausible argument. With one of them gone, what's to stop the other from bargaining from a point of strength, especially given Wallace's and Gasol's big deals.
From a rotation standpoint, I think it is much easier to replace Deng than Gordon. Noc, Thomas, Khryapa and even Sefo seem like adequate replacements, although probably not the same combination of size and athleticism that Deng provides. On the other hand, I don't see anyone replacing Gordon's scoring ability at the 2 spot, or on the entire team, although Gasol's contribution at the 4/5 will offset that some and should make things easier for all the other spots.
So I guess in my opinion Deng would be the better choice.