From Baseball America via Yanksfan vs Soxfan:
*Note: Due to the fact that this content is subscriber only, I am only giving you a portion of their comments.
Jim Callis: "In terms of pure stuff, I think Buchholz' curveball and changeup are right up there with Chamberlain's fastball and slider. I'd love to have either of those guys, but I'd take Buchholz"
Chris Kline: "They're both fearless, but Chamberlain pitches off his fastball more consistently. And not that Buchholz is some soft-tosser, but I when I think of an elite pitcher who will come right after hitters with pure power, it's Chamberlain"
Will Lingo: "I know they're talking about moving him to the rotation at midseason, but Jonathan Papelbon was a starter at this time last year too. I just think Buchholz is a little more likely to end up as a long-term No. 1 starter."
John Manuel: "Chamberlain's superior fastball makes him the better bet to be a long-term ace. In fact, it makes him the best pitching prospect to come around since I've been at BA, surpassing Josh Beckett and Mark Prior."