Digital for most things because it works very well for me for most things. I‘m not hung up on technology either way. I read mostly digitally these days, but physical books and newspapers are fine. Digital is particularly good for me with GTD, because change happens, and digital is easy to change. I use paper to mark up manuscripts (mine and other people’s) and for grading. I also use paper sometimes to explore technical issues and ideas.
Digital. I can access everything from anywhere plus I have shared lists for personal and professional things. I love paper, it’s just not functional for me with GTD. That being said, I do have an inbox where my SO and I throw things that need reviewing (those few things that come by mail, donation requests, coupons, etc) and we incorporate that in our weekly review.
My capture, lists, and simple project planning are paper based. I’ve tried to go digital on these but I am required to use different computer systems for home and work, internet is not always available, and paper is just faster and more flexible.
That is to say, I’m not adverse to digital at all. Most of my reference and working files are. My calendar is online and shared with family and colleagues. There are some types of work - long form reading, historical research, and journaling, where I have a strong preference for analog. Like @Oogiem ’s work, usually it’s if I need to need to reference multiple sources at once.