I have a 12.9” 2018 Pro. The same way I justify an 13” laptop instead of an 10”, which is a similar price jump. There’s a screen size threshold below which I’m not as productive. I use an iPad for most of my non-programming personal computing so I want that to be a good environment. 12.9” is the right size for me because of my height and arm length (same reason I use a 15” laptop.)

The variable refresh rate feels better on my eyes and the lightness of the 2018 Pros make them very easy to pick up and put away for their screen size, which is important to me because I don’t like the lethargy that sets in with laptops.