I have both as well as steering wheel controls
I use the buttons/steering wheel for FF/Next, Rwd, Play/Pause, Vol+/- and a few other functions
I use both inputs pretty much equally, but vol knob and steering wheel controls mainly for vol and skipping tracks. Everything else is pretty much touchscreen.
I found it distracted me from the road too much when driving to use touchscreen only. I went with buttons so I could control the main functions of music by touch for added safety.