I have to agree - The pencil is fantastic on the iPad, in terms of pressure, drag, control, and speed of editing. (Disclaimer though, I’m using the 2017 12.9 inch iPad model). In fact the pencil, and how strong it is as an editor, is why I am moving away from my stationary iMac. Occasionally, my selections disappear, so I have to zoom out, then back, for them to “show”. But this seems less an issue with the pen and more of the software or iPad processing power.
Comparatively though I have a Wacom pad for my desktop and hate that it captures pressure from the sides of my hand, and that I’m not editing on the actual screen. It all feels very counter-intuitive. I much prefer the pencil for the iPad.
One other note that might be helpful. My friend who also has the pencil for the iPad, and doesn’t do photo editing, doesn’t see a ton of value in the pencil and never uses it.