It is clear for everybody that PSN is not region locked, but many people including me have seen that online conditions are different whether you play with a game from your region or not.
I’m from Europe, and as far as I can tell :
-
Soul Calibur IV, whose online is already crappy, is even crappier with an Asia or US of the game
-
Street Fighter IV Asia has more delay than Street Fighter IV PAL
-
Tekken 5 : DR Online is “laggier” if you downloaded the US version instead of the European one
So may anyone explain me how it works ? But despite those problems, I have never had any problem for playing anyone from any region, only the online conditions are altered.