As a tangent, I find audiobooks offer a great multiplier to the number of books I can read. I'd say I get maybe 80% as much out of a book I listen to versus reading it in print, but I end up reading 3-4x as many books because I can listen while I bike to work, drive to errands, etc.
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 fiction, I get more out of audiobooks than print. There's something about hearing a story, especially from a good narrator, that just sticks in my mind and affects me more.
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.
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).