Same player cards / different stats; what gives
 

Seeing this more and more, and trying to find out why my competitors have these "buffed" card versions of the same cards I have.

Stuff changes depending on whether a pitcher is a starter or a reliever. Coming out of the bullpen usually increases the Stuff for a pitcher, though some select few cards can see a penalty. This change is applied (allegedly) in all circumstances, regardless of the pitcher's set position. Setting the position only allows the changed role to be reflected visually.