Difference in Asian CD's?

[Donna]

Sorry if this is the wrong forum to post in, I gave it as much consideration as I could

This may be a bit of a newbie question so please don't judge me but could someone explain the difference in Japanese, Korean and Hong Kong CD's of the same album? I've never fully understood - is there actually any difference in the sound quality and/or quality of the booklets inside?

I'm specifically asking in regards to Ayumi's albums. The prices fluctuate so much!