I voted Xander, Betts, Swihart and ERod. However, the poll doesn't really get at the nuance of my thinking.
Betts is in a league of his own. He is cost controlled for six more seasons. He appears to be a guy that can roll out of bed and contribute at a high level on both sides of the ball. It would take a supreme overpay for me to let him go.
Xander and Swihart are a notch below for different reasons. I have concerns about X's defense at SS and plate approach and Swihart hasn't proven himself for a long enough period at high levels (no fault of his own) and still has to develop his hit tool. However, between their team control and ceilings, I would only consider moving them as part of a package for a cost controlled ace with a pitcher's frame and good mechanics. I would also be less willing to move Xander than Swihart because of the presence of Vazquez making Swihart potentially more expendable. If Marrerro continues to establish himself and progress into a player similar to Vazquez, I'd view them similarly.
I chose ERod as my 4th. However, he occupies the next level down with Owens, as the Sox best starting pitching prospects. I have a strong preference to ERod over Owens. This is because ERod is younger, has a power fastball and three pitch mix and this makes me believe that he has fewer constraints facing him to become a top of the rotation pitcher. Whereas, I have more concerns that Owens may max out as a middle of the rotation guy because his stuff may not play at higher levels, he's up in the zone often and he lacks an MLB quality 3rd pitch. For these reasons, I'd trade Owens in a deal for a player at a position of need that I really like but do not love. To illustrate, if Ruin Tomorrow was willing to move Hammels for a package around Owens, I would jump at it, but I would not jump at a the same deal if it featured ERod instead of Owens. However, if the Sox could get someone of the ilk of Cueto or Zimmerman and they were open to an extension (which I understand is unlikely), I would be willing to build a package around ERod.
Just below that I'd place Devers, Margot and Chavis. These are three guys that are young and have shown a lot at lower levels. However, I'd prefer to see how they mature. As another poster above pointed out, if you wait a half-season or more, these players may substantially enhance their value. Granted, the flip side is true and they may go from young blue chip to a lotto ticket. However, I am optimistic, based on their tools and the scouting reports on them, that these guys are more likely to evolve into guys that are Betts/Swihart/Xander level "untouchable" or a guys that you can move for an elite player than they are guys that you are going to regret not moving in 2015.