I'm a vintage machine guy. None of my machines have the start/stop feature. I'm also the oddball here because I prefer a knee control over the foot pedal, the knee control never moves around on you. I'm not sure I would like the start/stop button. I like the instant feedback of either a foot control or knee lever. There's no lag time while you're reaching for the button and I can keep my hands on my work. If I want even more control I'll turn the machine by hand.
Rodney