Essentially what the staff is likely arguing is the idea of win now or win later.
It's important to understand how the staff views each of the players.
Vaughn is definitely a win now player. His value decreases with each year as his age increases. There is no hope of "developing" a player like Vaughn. He is what he is.
Hairston is likely viewed as a win later player. One can assume that he will have an appreciating value to the team and that the dividends from his development likely wouldn't be felt this year.
I'm curious how the staff views Farmer. He obviously has the ability to score right now, but would he be able to overtake even a player like Finley? That still leaves Bowen/Udoka/Mason and eventually Ginobili in front of him even if he does. But hes young, so developing him is likely a draw as well. So maybe hes something of a blended now & later kind of guy?
With that aspect analyzed, what will each of these players bring to the team?
With Vaughn being a win NOW guy, and assuming Hill overtakes him, as well as a deep reserve he really contributes very little. Vaughn stands as a hedge against two things: injury and Hill contracting "Beno-itis" or otherwise hitting the rookie wall. And concerns over Hill are most definitely well-grounded. There are concerns about how he'll adapt (coming from a small college) and that his summer league appearances were often pedestrian. I think Hill will be good, but how good will he be this year? Jacque also was initially brought in to mentor both Parker and Beno. If ever there was a PG that needed mentoring it was a youthful one like Hill. Overall, Vaughn is their ace in the hole in case something goes south with any of the PGs, but especially Hill.
With Hairston being a win LATER guy his production is largely deferred. Hairston symbolizes a look towards the future and an anticipation of continued success.
Farmer being a blend offers an interesting situation. His win NOW aspect helps the team in a crucial area, but is probably little more than an injury hedge. And in the unlikely event that he makes the team and is active he also serves as a drought-buster. His win LATER aspect suggests that he can eventually take up the mantle held by some of the elder statesmen on the team (Finley?). Although, I'd say his ceiling is significantly lower than his compe ion's.
What are the team's motivations?
Obviously we want to win a championship. Now. Which lends itself to the win NOW players. Vaughn and to some degree Farmer, help this perspective.
But how long do we think the window will be open? Surely for a few more years at least. And our current wings are aging rapidly and probably won't be compe ive as long as Mr. Duncan is. Bringing along quality wings enables the team to keep supplying Duncan with quality support to make the most of his now limited contender years.
So the basic question is, does Vaughn give you enough NOW to dismiss the potential future of those two wings? And do those wings have enough potential for LATER to make up for Vaughn's current hedge?