Bottom line is this: The players with the most trade value (from the point of view of other teams) are Jason Richardson (who, IMO, is untouchable if your the Warriors) and Troy Murphy. Murph puts up numbers that are worth the price of his contract.
Dunleavy, on the other hand, is going to be difficult to move, considering the contract extention he signed before last season. His contract is your proverbial 'poison pill'.
Personally, I think if the W's are going to be successful, they need players that will remain dedicated on the defensive end of the ball--neither Dunleavy or Murphy is that type of player.
In other words...I say trade 'em both. Dunleavy has, as traditionone said, has underachieved and can probably use a change of venue to try to reinvent his NBA career. Murphy, while decent offensively (even though he has a rather low FG% for a PF), hurts the Warriors defensively. Besides, the W's have Ike Diogu in the wings to take over the PF spot. If you can get value, trade Murph as well.