I have a touchscreen and a IR Remote. I find myself using the remote between 95% to 97% of the time. I use the touchscreen maybe 3% to 5% of the time at the absolute very most. The remote is just more convenient and comfortable to me especially for switching tracks, volume, FF, RW, Pause, ETC. It's to the point where I am considering gutting the touch overlays on the new system I am currently building so I won't be sacrificing brightness and adding glare just to look cool "Playing Iphone" touching on a screen.
I get pounced on by forum members everytime I say this but......
I just don't find myself using the touch screen feature enough.
Personally if they sold VGA displays without touch overlays any cheaper, then I woud just go that route instead.
All jokes and rags aside, I think it's more of what input devices work for you, than what other people think will be good for you. Build your Car PC around you. Spend a good portion of your time brainstorming on input devices. Remember the point of the car pc is to make time in the car more easier and tolerable, and your pc build should reflect that.