I don't like a one button solution. I like a physical switch so I know when I flip it the AC is cutoff. Then extend the PC button out to right beside the switch. Works great on my vpin I reach under and flip the switch in the same location as a real pinball and then press the button beside it all in one second.
My vertical cab is setup similarly. There is a on/off switch at the PC-style (removable cord) power intake at back, with an LED (and fuse) built in so you always know the status.
Once this mains switch is on you can press the momentary button that turns on PC which then, via 5v triggered relay, routes power to the rest of the cab. Same button initiates orderly shutdown and turns everything off automatically once that is complete.
There is also an old-school flip-switch for power, inside the cab door, which I retained for nostalgia (I re-made from an old cab) and wired in. But in practice I don't use this one, it just stays on.
My brother-in-law uses this vertical cab more than I do, almost every day (his fave games are Flying Shark, Contra, Arkanoid). He is not a complicated or technical man. Yet he is happy because the cab is so easy to startup and shutdown. He doesn't need to ask me for help or anything - just connects power (if not already connected) and presses then button. Game on!