Looking at the most recent rookies to make the jump to the majors, it seems as though pitchers have the most impact in there first season as far as fantasy goes.
Have to disagree with you there. Every rookie goes through an adjustment phase once they get to the majors - and more often than not that adjustment phase lasts longer for rookie pitchers than rookie hitters. Recent examples of rookie hitters making a big impact right away: Braun, Soto, Votto, Longoria (starting to heat up), and it certainly appears Bruce (book is still out of course, but hell of a debut). Recent examples of rookie pitchers struggling: Andrew Miller (top pitching prospect a couple years ago) and Cueto. Even Lincecum and Hammels had adjustment phases. It seems like the better and more talented the pitcher the less time it will take to adjust - but there will
be an adjustment. Extremely talented rookie hitters seem to have little to no adjustment once they reach the bigs. Add that managers are careful with rookie pitchers pitch counts, and you have to conclude that rookie pitchers are less equipped to contribute in a significant way immediately.
TOP PROSPECT Rookie starters that come up at some point during the season tend to be more effective then hitters. You chose Andrew Miller? But forgot Recent successors Felix Hernandez, Jered Weaver, Matt Cain, Justin Verlander, Jeremey Bonderman(until he blew up) Francisco Liriano. (Tim Lincecum, Cole Hamels)
My argument was that top prospect pitchers who are brought up once the season has started tend to be more effective then hitters. Pitchers are ready to go when they come to the majors, where hitters need to make adjustments.
As far as a learning curves go it doesen't matter if it's in the same season as long as they over come it. I would consider Lincecums season a successful one last year.