Most touch screen panel mount avionics provide some kind of anchor to connect the static part of your hand to operate. (Rest your thumb here or pinky side here and operate with the index finger.)
I was worried about the issue, but in light turbulence, it’s no issue IME and in moderate, it’s maybe less certain than knobs, but I bet even there that I could still enter an accurate flight plan update, whether a new full route and just a direct-to shortcut) faster on the touch GTN 750 than on an old (multi-knob) GNS 530. (That’s not just touch; it’s partially the discoverability and access to “more than the -D-> key” functions.)
I am glad the critical autopilot inputs (HSI heading bug) and other flight controls are not touch, though.
I like the anchors - but I use them to anchor me for pushing the hard buttons and twisting knobs instead. Of course, I personally avoided putting in (mostly) button free avionics like the mentioned Garmin GTN series in my plane. I fly them in other planes, and they are well featured, but I just personally prefer hard buttons.
Also, knobs in turbulence are fun. "Turn left 15 degrees" can become a random amount on your heading bug with an unfortunately timed thump!
Anyway, bottom line is that I find it easier to see the relative angles and trends of the pointers in old analog gauges in turbulence than read the tapes. The angles meant something easily interpreted as being unexpected at a glance even if the absolute value might take another moment to read.
Imagine if our AI were two tapes, like the EFIS horizontal and vertical deviation indicators!!
I was worried about the issue, but in light turbulence, it’s no issue IME and in moderate, it’s maybe less certain than knobs, but I bet even there that I could still enter an accurate flight plan update, whether a new full route and just a direct-to shortcut) faster on the touch GTN 750 than on an old (multi-knob) GNS 530. (That’s not just touch; it’s partially the discoverability and access to “more than the -D-> key” functions.)
I am glad the critical autopilot inputs (HSI heading bug) and other flight controls are not touch, though.