I think both have very good chances to become major leaguers and were both part of a very good draft class by the Red Sox in 2005. Bowden has the higher ceiling of the two and I think he arrives sometime in late 2009 or early 2010.
Here is the scouting report on him.
Bowden has an arsenal of four MLB caliber pitches: a low-90s fastball which tops out at 95, a 12-6 hard breaking curve, a tight slider, and a plus circle changeup. Bowden is said to be a workaholic and just loves to pitch - another player who just lives and dies for baseball. Very athletic. Absolutely dominated high school competition in 2005. Delivery is not as smooth as it could be.
Here is a quote from Bowden on his delivery from Red Sox nation:
"The team sent me to ASMI (the American Sports Medicine Institute), in Alabama, which is the biomechanics lab run by Dr. Andrews. They measured my timing to make sure there's no additional stress on my arm. The results came back very well, so they don't feel I need to change anything. I do have to pay attention to my direction to home plate though, because I push off on my toes more than my whole foot. I'm facing a little toward right-handed hitters in my delivery."
Buchholz I could see depending on how quickly he moves through the system up by late 2008 or early 2009. He is another pitcher who throws hard. Buchholz has a mid-90s four-seam fastball, a two-seam fastball, a slider, curveball, and a circle change.