Normally, I'm a Pro Evo fanboy and don't usually, but I have to admit than FIFA 09 is better than Pro Evo 09 in terms of gameplay. The graphics are better too. FIFA obviously has a wider array of leagues. I mean, nobody cares about the K-league, but they do have the German league for example, which Pro Evo doesn't have. Pro Evo's setup is still better and the formation settings are more in depth. FIFA's player attributes are normally terrible too.
I'll probably buy both for 2010 anyway.