In a pre-game interview before a recent interleague game, Giants manager Bruce Bochy was asked which league's team had the advantage with the DH rule. To my surprise, he said that the AL team had the advantage, because they use a very good designated hitter that was signed for exactly that purpose and who is in the lineup every day. The NL team has to fit a bench player into the lineup.
I agree with him, and wrote about this a few years ago. I'm wondering if the conventional wisdom is either changing or has changed in baseball. I haven't heard an argument about the DH in quite a while and certainly haven't heard the "AL is penalized in the NL park by having a bat taken away, while the NL team gets to add a bat in the AL park" line of reasoning either. I hope the view of this is changing for the better.