It's hard to judge farm systems.
However, I'd go with upside more with position players, with shorter benches it's "you win or you die" for most of these guys other than backup catchers and jack of all trade types - if a hitter isn't pounding the ball by their third minor league season or so, he's in deep trouble. One reason I'm ready to give up on Ortiz, he's young, but I'm getting a Cozen's vibe - he'll put up big HR numbers but never make consistent contact. If you're not putting up .800+ OPS in AA and .850+ OPS in AAA, it's hard to project you as a ML starter these days.
Pitchers are different b/c there is value in 4th and 5th starters and RPs, so both the big arms and the smart arms have value. And pitchers can emerge with tweaks, develop a secondary pitch, movement on your fastball etc., and you can make a big jump very quickly. Sometimes it comes from filling out a thin body, sometimes mechanical tweaks, sometimes a new grip. Hitters, once they physically mature, rarely make big jumps. Either you got it or you don't.
So you want depth with pitchers, quality with hitters.
