You only have time to read 300-3,000 books in your life. Pick wisely.
They also force me to stay focused while I'm listening, versus how my mind tends to wander while I'm reading a print book (where I realize I've been on the same page for five minutes).
For non fiction, I'd probably agree with your 80% number. I generally prefer print in those cases, where I can easily highlight important sections and take notes.