There's more to it than the NL West parks, actually, though that's also a factor. Studies have been done that long-term Rockies hitters really suffer on road trips, particularly early in road trips. Just as Rockies pitchers suffer from breaking balls not breaking at altitude, hitters suffer from seeing different pitch mixes and breaking ball tendencies between Coors and road parks. I'd have to dig up the study but there is a significant detriment to Rockies hitters in the first few games of a road trip. On a long home stand, Rockies hitters tend to see a lot of fastballs that move differently and they get into bad habits. Then they hit the road and see a bunch of breaking balls that move a lot more. The adjustment is difficult for hitters, just as it's difficult for pitchers. Using either home or road stats to project Rockies hitters is a mistake, as their true talent level usually sits somewhere in between the two.