Smartphone/app/whatever control is simply not an option IMO as the primary control input for a system where real world hardware can be damaged if you lose control. I don't want to by typing in a passcode, waiting for my phone to update, closing out whatever popup is up at the moment, etc. while a train is running off the track. There's a reason nobody operates industrial machinery like cranes with a smartphone.
I use both dedicated remotes and touchscreens on my layout. The touchscreen is nice, and can speed up some things like major switching operations, but is never used solo - it is just a compliment to the dedicated remote.
I run DCC, not DCS, so I'm not directly impacted by the current conversation. But I will say, if you're looking for options, it's worth considering. PS3 locos support DCC out of the box, so that part is easy.
The NCE remote, complete with hardkeys. 
And JMRI on an iPad with a scale layout map with touchscreen control for turnouts, macros, accessories, etc.:
