There are some good use cases for larger iPad
I found an app that allows me to use my iPad as an external monitor using the usb 3 cable on my macbook pro. I was very pleased when i discovered that it also worked when using VMWare running Windows 7 Professional.
This gives me a whole new perspective on the iPad Pro. It can act as a tablet, a mobile external monitor, an adjunct device for reference all while you're on your laptop, an artists drawing board, a software designers drawing board, reviewing and marking up documents using the pencil, and then on top of that, if you need to go to a meeting, just grab the iPad and the pencil and off you go.
To me this spells mobility, power and convenience. Incidently, the app has both Windows and OSX clients, so you're not restricted to just one OS for your laptop. I'm not sure if i can mention the product name on here, so will refrain from doing so.