In vaccum, meaning free from context - or situation, Hafner is having a better year. However, when context is added, meaning what situations the production occurs in, Ortiz is far and away better.
VORP - context free
Hafner ~76
Ortiz ~60
WPA - Win Probability Added
Ortiz 6.9
Hafner 4.2
Ortiz has meant much more to the Sox than Hafner has to the Guardians.
EDIT: And, when we are talking about two guys separated by ~.040 OPS, I want the one who's doing it in more crucial situations.