The US and European PSP bundle is exactly the same as the JAP bundle, except it comes with English instructions, demo disc, and a cleaning cloth. Depending on when and where you get your PSP, it might also have a different firmware version. New PSP consoles will have the latest firmware version available. The contents of the Demo Disk may also vary depending on time of purchase.
Some people suggest that JAP PSPs have a better TFT Screen than US or European PSP, but this is not the case. Any TFT screen is just as likely to get dead/stuck pixels.