I use a foot pedal. I found recently that giving my other foot a higher place to rest made my body more comfortable.
I also love my knee lift on my Bernina (it was on my list of must haves when I bought the machine 20+ years ago). I haven’t used a knee bar for power since I sewed a bit on my grandmother’s cabinet, which was probably more than 40 years ago.
My machine doesn’t have a stop/start button so I can’t say how I would like using that (although for work like chain piecing or FMQ, where I stop and start a lot, I can’t imagine I would like needing to use my hands to control the speed).
Finally, I recently discovered that my machine behaves better when I don’t use the flywheel to advance the needle with fabric under the foot. I’m much more likely to get a rat’s nest of threads if I use the flywheel. Better to just tap the foot for a single or half stitch.