Why the heck would you bother getting a japanese version of something when:
1. You're not able to understand such language.
2. You can get one in your own language.
Apart from a collector's point of view, there are no reasons to do so, first, your GC can run any region disc, and the GBP hardware is region free (only its disc isn't), second, Swiss is now able to run the GBP boot disc ISO from an SD card, so you can judge wether you need it, or better go with GBI. Guess what's my guess?
