My main devices used in a day are my iPhone 15 Pro (6.1”), MacBook Pro (13”), and iPad Pro (12.9, now 13”).
My MacBook basically turns into a desktop and I sit down there when I have to get stuff done, have a typical office work flow.
My iPad i keep in the living room, pick it up to do quick tasks, and travel with it generally. I use it with the Magic Keyboard a lot of the time, but also take it in and out of a Zugu case when I expect the use to be more along the lines of content consumption.
How did I decide between the 9.7/10.5/11” form factors vs. 12.9/13”? I had both and after a year, the smaller iPad was collecting dust. I’d almost always just use my iPhone for anything I was thinking of using the 11” iPad for.