I don't know what you mean by this, but there's no benefit from trading Pokémon between US and EU games.Thus making trades between the 2 better for both party's?
Oh really now? And why is that? Because it might be in a different language? I for sure know that the Japanese one is different from the North American version not only because of the language change (duhz) but also, because theres special pc wall paper. I'm refering to the 4th gen game. I might be wrong, it might be the Europian version but anywho. Its called Asinastra, its the background of Palkia and Dialga obtainable in those region games only.European games are different from american games.
I thought I remember reading that if you obtain a Pokemon from a different country and breed it then it is suppose to increase your chances of hatching a shinny. I don't know if this is the type of info you were looking for though