He hasn’t even thrown 40 major league innings. And any scout will tell you that Buchholz has much better stuff. There is no way Buchholz is “trade bait.” He is still the top pitching prospect in the organization.

Buchholz is a year younger than Masterson, and has been much better in the minors (career numbers):

Buchholz (301.2 IP) 2.51 ERA 1.03 WHIP 11.06 K/9
Masterson (229.2 IP) 3.77 ERA 1.19 WHIP 7.42 K/9

Here are the scouting reports on both pitchers from soxprospects.com:

Buchholz:

has a low-to-mid 90s four-seam fastball, a two-seam fastball with decent movement, a slider, a hard 12-to-6 curveball, and a change-up. In 2006, Buchholz actually let loose towards the end of the season, when his fastball was sitting around 96 mph. However, over the course of the season his fastball typically sits around 91-94 and tops out at about 97 mph. His plus change-up is generally a straight change that sits around 78-82 mph; he also throws a circle change. His curveball, the best in the organization, sits between 76-81 mph with a knee-buckling bite. On any given night, Buchholz’s curve or change can be unhittable, and he tends to rely on whichever is on as his out pitch throughout the game. His slider, while average to above average, is a bit behind his other secondary pitches and sits in the low to mid 80s. Mixes in all of his pitches phenomenally. Good demeanor on the mound. Pitches well under pressure, pitching coaches have said he has ice water running through his veins. Nice pick-off move. Struggled with consistency early in his pro career, but otherwise has ace makeup. Might need to add and maintain some weight to endure a full major league season.

The pitcher they compare him to: a righty Cole Hamels.

Masterson:

Big righty with an ideal pitcher’s build. Dominated the Cape Cod League in 2005. Masterson has a three-quarter delivery with a slinging-type motion. His arsenal includes a sinker, a slider, and a change-up. Of those pitches, his best is a phenomenal plus-sinker with an excellent heavy drop—he can vary its speed from 84-94 mph, catching many hitters off balance. Also mixes in a very good slider that sits in the low 80s, and an improving 77-81 mph four-seam circle change. Uses his sinker predominantly as his out-pitch, but also can make use of his secondary pitches to get out of jams. Could stand to mix in his changeup a bit more. His mix of pitches results in a high groundball-to-flyball ratio, getting a lot of double plays. Very good command of the zone. Prepares well for every game and pitches with confidence on the mound. Good fielder with a quick and deceptive pick-off move. Strong character, Masterson is one of the most likable persons and teammates going. Converted to a starter in 2007 after coming out of the pen for Lowell in 2006, may still project as a reliever at this point depending on how well his change-up progresses. Needs to work on keeping his delivery consistent deep into games – he’s struggled a bit the third time through lineups. If he moves to the pen, Masterson will need to keep the walks down and improve his ability to pitch out of the stretch. Ultimately, Masterson’s ceiling is a #2 starter or a dominant set-up man.

Pitcher they compare him to: Derek Lowe.

To give up a potential ace pitcher who is not yet 24 for an expensive pitcher with tone of wear and tear like Sabathia is crazy. Even crazier, is the notion that a deep team like the Sox needs another arm, especially one that will likely be very expensive and isn’t one of the top ten pitchers in baseball.

Masterson has 2 pitches, one being his sinker that are fantastic and a very nice 3rd pitch. Buchholz will not establish his fastball and relies far too much on his curveball/change up combination and hitters in the MLB have figured this out.

again this is only my opinion, but if the Sox were to take one or the other and put them on the staff I would rather have Masterson.

Most likely than not, Buch will still be our ace.