I need some advice

[Ninja_Gaiden]

Guys am planning to buy a PSP but am wondering which is the best US version or JAPAN version, I found some info about the screens (US: Samsung screen and for the JAP: Sharp screen) and they said sharp better, that is the only difference I know so am asking if some one has more differences please tell me

I want to know if I can play Grand Theft Auto Liberty City Stories online or its only multiplayer (not online)?

Did any one try NFS: most wanted for PSP and is good ?