Last year, MLB 2K9 rubbed plenty the wrong way when park dimensions and outfield signage seemed blatantly reconfigured to accommodate larger in-game ads. New screens for two parks seem to indicate the game scaled back that kind of aggressive design.
In MLB 2K9, Wrigley Field sported a large, translucent sign for in-game sponsor State Farm to the left of the stadium's iconic out-of-town scoreboard. It now appears to be gone (with more buildings forming the skyline behind it.
Nationals Park in Washington also had its dimensions altered, most notably to the left-field bullpen and the height of the left field wall. Such things can of course affect balls in play and therefore gameplay. MLB 2K10 has brought the measurements more in line, and even cut down on outfield signage beyond the reach of balls in play.
Pasta Padre has a good comparison of both stadiums, MLB 2K9 to 2K10, with images from real life thrown in.
MLB 2K10 Fixes Advertising Altered Stadiums [Pasta Padre]