I'd go for a larger touchscreen, if you can, although 24 is a wee bit bigger than mine. And I just upgraded to the last version of Cake, so I haven't checked out the new features. But in general, "touch" is great for many functions, but it is not a replacement for the computer keyboard (I hate having to try to type without tactile feedback) or as precise as a mouse. You'll still need to use both of those. I prefer a synth keyboard to Cake's virtual controller, but it certainly works. You can do a lot with touch, but it shouldn't be thought of as the sole input device. I keep my keyboard on my lap and mouse within reach.
But hopefully touch will continue to be integrated into SONAR, so it can be the main input device. Except for typing. With touch, it would be great if most Cake controls you touched could "fly out" to be larger. They are going to have to continue to improve and probably re-jigger the interface for easier touch control before it can become the primary method of control.