Stop Jap Naked is a remastering. The overall sound quality is a lot 'cleaner', the bass and drums are a lot louder, and I believe that some of the lyrics have been changed, but apparently there is an actual reason for that. There are a few other, really minor, differences such as the buzzer at the beginning of track fifteen has been replaced with a loud police car siren, and they also added the siren at the end of the track as well.
New to punk? Japan has always been a huge exporter of great influential punk, especially hardcore. The American and British rock press just never wrote about it. Though expecting the British music press to write anything truthful about punk is also a little too much to ask.