Ive got opinion on the minipac.... get it. Seriously, the minipac is wonderful and Im constantly backing it up over other products. The difference between the two is really size and the trackball support... the minipac has more than enough buttons, 2 joysticks, the shift function and a trackball / spinner interface!
Seriously, its the perfect product IMO for arcades and the price is right... now as for grounding:
- each button has a ground on its microswitch (as stated). One of the best ways Ive found for grounding would be to just get one long ground wire that goes from the minipac to all of your buttons (through eachother) and back to the minipac, sorta like this:
MINIPAC -> BUTTON -> BUTTON -> BUTTON -> BUTTON -> BUTTON -> BUTTON -> MINIPAC
That way, if a ground is faulty, you will definately know which button(s) are causing the problem, because all the rest will still function, whereas at the same time, you save all that time wiring everything (like 30 wires) to a central space, which causes alot of clutter. Go out and buy a few feet of cheap green wire for like a dollar (not at like radioshack, i dont get why all these people go out and buy top-of-the-line crap for like 15 bucks when dollar stores have the same!) and just cut it to lengths long enough to go between buttons. Make like a chain effect with them and just link them all together......