First off, congrats on a gig in Japan!
As for two prong, it will give you floating ground. Some modules won't work correctly or not at all, with with a two prong power connector. You should be able to pre-flight check that with a two-pronged PSU. I use a two prong Toshiba notebook brick with a Tiptop uZEUS and Make Noise René doing all kind of weird things got me hopping mad.