I don’t really detect a difference between US and Japanese HRAP’s. They’re basically the same thing. Minor color differences yeah, but it’d be too expensive and just not worth it to change everything else.
What I have noticed changing are the arrangements of the buttons between the earlier HRAP 2’s and later series in the run like the HRAP 2 SA whose button layout is used on all HRAP 3’s as far as I know. License sticks like the Tekken 5 and Arcana series use the earlier button layout but unlike real HRAP (license sticks only use the base and power cords; insides and most button/stick components are different) have the buttons soldered into the PCB board.
I can deal with either layout personally. Not a big deal to me.
What I DIDN’T like was the changing of the screws from ones you could externally remove with a hex tool to a new screw (T5 / HARP 3-style) that forced you to remove the stick base first before you can remove the hex nuts from the new-style screws. While it’s not difficult to remove a T5 stick base it’s less convenient that getting automatic access to the pushbuttons’ undersides via the faceplate the way you can on a HARP 2 SA for iinstance.