""If it's turbulent, its not going to be easy to push any buttons touch screen or not.""
If you have used a touch screen system in flight in a small aircraft you probably would not have the same opinion.
A normal button has a feel to it, can take a bit of stabilizing pressure prior to activation and you can usually rest the other fingers on the surround while touching the button.
A touch screen has no feel, no give for that sudden touch when the turbulence hits. If you touch the screen with any of the other fingers you get an unintended response.
I built a Jabiru and installed a touch screen monitor with a computer that runs "AirNav VFR" a moving map/flight planner with the australian aviation maps with gps position markers etc. I have had the system for a year and now I almost never even turn it on. I use a Garmin 296 in preference.
I have pretty small hands but I still find that inadvertant triggering of adjacent buttons is very common. You can bet that the aircraft will shudder just as your finger hovers over the screen button.
The slightest bit of turbulence and you have a lot of trouble getting your finger right and a slight miss hit turns on some function you didn't intend and you then have to back track (if you can ).
I found I tended to keep stepping further away from what I wanted to do.
I personally would not spend money on any system that was touch screen again. Unless I built a homebuilt 747!