The first guy. The scouting disparity and signability issues aside, the only real stats that would put the second guy ahead of him are overall rating, splits and durability/health.
While I tend to be a fan of high splits, overalls are relatively worthless, and the first guy is still very good for those stats which tend to inflate a player's overall. There isn't much of a drop-off already, not factoring in what the difference would be after signing him.
The first guy can play up middle for you, the second guy probably is a 3B long-term.
Not to mention higher patience/make-up seems to have a huge impact on how close a player can get to his projected ratings.