Since Oriole Park at Camden Yards (generally considered the first of the "retro parks" which not predominate) was opened in 1992, baseball has introduced 20 new ballparks (18 brand-new stadiums, and 2 expansion sites) which are currently in use. From that group, I looked at the teams that played at the most friendly hitter's park and pitcher's parks. I left out the preponderance of parks which were either more or less neutral or haven't been open long enough to show a consistent advantage.
Baltimore Orioles (Camden Yards) - 16 seasons, 4 winning seasons, 1 Div., 1 Wild Card, 0 Pennant, 0 World Series
Cincinnati Reds (Great America Ball Park) - 6, 0, 0, 0, 0, 0
Colorado Rockies (Coors Field) - 14, 5, 0, 2, 1, 0
Detroit Tigers (Comerica Park) - 9, 2, 0, 1, 1, 0
Houston Astros (Minute Maid Park) - 9, 7, 1, 2, 1, 0
Philadelphia Phillies (Citizen's Bank Park) - 5, 5, 2, 0, 1, 1
Texas Rangers (Ballpark at Arlington) - 14, 5, 3, 0, 0, 0
73 seasons, 28 winning (38.4%), 7 Division Titles (9.6%), 6 Wild Cards (8.2%), 13 Playoff Appearances (17.8%), 4 Pennants (5.5%), 1 Championship (1.4%)
Cleveland Indians (Progressive Field) - 14, 9, 7, 0, 2, 0
Florida Marlins (Dolphin Stadium) - 15, 5, 0, 2, 2, 2
Los Angeles Angels (Angel Stadium) - 12, 9, 4, 1, 1, 1
San Diego Padres (Petco Park) - 5, 4, 2, 0, 0, 0
San Francisco Giants (AT&T Park) - 12, 8, 3, 1, 1, 0
Seattle Mariners (Safeco Field) - 9, 5, 1, 1, 0, 0
67 seasons, 40 winning (59.7%), 17 Division Titles (25.4%), 5 Wild Cards (7.5%), 22 Playoff Appearances (32.9%), 6 Pennants (9.0%), 3 Championships (4.5%)
Obviously, many other things factor into a team's success, but when you look at this relatively large cross-section of data you can see why the Yankees and their fans would prefer that their stadium not be "Coors Field east" as some have been calling it. Teams that play in pitcher's parks are 20% more likely to have winning records, almost twice as likely to make the playoffs, and three times as likely to win World Series.
There may be several reasons for this. There is the cliche, "good pitching beats good hitting," a motto emphasized by teams like the Giants and Padres who have stayed competitive in many recent seasons despite have very mediocre offenses.
There is also the pragmatic conclusions voiced general managers in Texas and Colorado, that the top free agent pitchers don't like to go places which are inherently dangerous to their ERAs. So, teams with hitter's parks end up overpaying for guys like Mike Hampton, Kevin Millwood, and Eric Milton. Meanwhile, teams with pitcher's park get deals on pitchers trying prolong or rebuild their careers, guys like Randy Johnson, Greg Maddux, Carl Pavano, and Randy Wolf. And young pitchers can have their confidence ruined by fly balls turning into tape-measure blasts. Just ask David Nied, Jeremy Bonderman, or Brandon McCarthy.
Chicks dig the long ball, right? Inflated offensive numbers also means inflated salaries for hitters. Not only does a team like Colorado have to overpay to lure pitchers, but they have to hand out obscene contracts to keep players like Todd Helton, Matt Holliday, or Larry Walker. Great hitters all, don't get me wrong, but playing in say, San Francisco, for the bulk of their careers would've cost each of these guys millions of dollars.
While the general managers in pitcher-friendly environments can compensate to some extent by building around speed, defense, and gap-hitters and have consistent success, a similar formula has not yet been found for the hitter's park. Perhaps last year's Phillies will be the model. However, the struggles of Cole Hamels, Brett Myers, Jamie Moyer, and Brad Lidge to begin this season may be another sign of how difficult it is to win consistently in a launching pad. If Yankee Stadium maintains its current homer-happy pace, I expect their will be serious renovations in the offseason. That may be the easiest and more inexpensive way to prevent themselves from becoming a power-laden .500 team.