After years of only doing remote gaming, I've settled into a very specific relationship with PDFs.
-If I'm looking for rules during play or learning the core mechanics of a new system, PDFs are fine, and even preferable for me.
-If in-depth, linear reading is required, PDFs are a slog--like Snarf, I can't read a single digital document for long times at a stretch.
For example, the current edition of Delta Green is, to me, something like a masterpiece, and I enjoyed it in bits and pieces as PDFs. Then a friend sent me the slipcase (hardcovers of the Player's book and Handler's guide) and suddenly I was reading it like a novel, devouring stuff like that massive, beautifully-written-and-laid-out timeline of the organization in a way that my brain just couldn't on the screen. With PDF's I start skipping around on autopilot, looking for juicy little tidbits here and there, like some addled, third-act Lovecraft character who can't properly focus on any one damn thing. So to the degree that I sit down and read gaming material for pleasure, rather than straight prep, print is way more fun and efficient, but in a pinch I'll pop around in a PDF for random hits of enlightenment and dopamine.
But when it comes to using rules or adventures, especially while GM-ing, I'm all in on PDFs. These days I have about five different PDFs in minimized windows ready for checking, while my print books are across the room, prettying up the joint.
(And for context I am an old, in my mid-forties)