HAPP buttons (the buttons GGG currently offers) are made in the USA. I even know the name of the injection molding company where the tooling lives.
As for button quality, the HAPP parts are definitely more solid in construction. The X-arcade buttons have a somewhat looser hold on the microswitch, thinner walls on the plastic parts (this is most evident in the plunger part), a finer thread pitch (more turns required on the nut) and are shorter. But the fit and finish are fine and with a good Cherry microswitch installed, one would not be able to tell the difference from above the panel in actual appearance or operation.
Are they "Real arcade parts"? I think that might be a little bit of a stretch, but if it walks like a duck and quacks like a duck.....
As for the X-Arcade trackballs, they seem to be very similar in appearance to the Betson Imperial. The photos I have seen look almost identical, with only the Imperial name missing. The square frame was still in the same spot, but without the name in it (*edit* Apparently it was a pre-production unit as the units carry the X-arcade logo there now). One would really need to dissect the unit and compare the internal components to know for sure how the quality compares. I've seen some poorly made 3rd party replacement rollers for the Betson trackballs, so the rollers would be a good place to start the comparison.
I haven't actually used one of the trackballs, so I can't comment on the performance.
RandyT