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The argument about the DH rule only benefiting the AL team in their home park doesn't hold water, at least not all the time. In my estimation, this world series was just as influenced by the DH situation in Colorado as it was in Boston, for the simple reason that Boston went from having an extra (great) hitter in the lineup to having a bench bat far better than any NL team could realistically carry.
You could argue that's just evidence of the Red Sox superior depth, and in a way you would be right. But it's a structural advantage. How many times did the Rockies start to rally only to be faced with the bottom part of their order and eventually their pitcher? If they had Youkilis as a bench bat in those last two games, I think there's a pretty good chance the Rockies could have come away from the series with a victory or two.
I agree there's so much going on that a statistical argument is likely to be pretty difficult. And it's not an advantage that's going to pop up every year, because of roster construction issues on the AL side (and the occasional phenomenally deep NL team). But AL teams have a strong incentive to have one more excellent hitter on their team than NL teams do, and that matters in NL parks as well as AL parks.