Some stuff must be digital of course but I always find paper notebooks superior in the end. Something about physically writing it down makes me remember it better. And even though they can become disorganized I like occasionally flipping through an old one - it often triggers memories associated with the time I wrote the note or people I worked with that I would not get with digital files.

I think the other thing is it forces you to be more space conscious - you do not have unlimited real estate. Large notebook for some things, smaller handbook for portable, and notes that are compressed or adjusted for each.