I think he will break out of his slump and should improve his numbers around the board. However, I think a lot of pre-season projections were a bit too optimistic regarding Green, and don't see him as a true elite of. Solid, but not elite.
Hernandez is a bit of an enigma. If he keeps pitching this way, he definitely ranks among the top AL starters, even if he does continue to give up too many homers. Unfortunately, it's also quite possible that he'll implode...
If both sides are filling needs, I'd say it's good for both, and may even be great. If each owner is gambling on the player they believe will prove to be better, you can't really argue with that.
If you're asking which player is better overall, I'd lean toward Hernandez at the moment (but not by much) and hope he stays focused, but that question is irrelevant if both sides can fill a hole here.