Well... I can tell you this much about the FLP audio: Because of Feynman's use of gesture, demonstration equipment and (most importantly) the blackboard, it is impossible, particularly for a beginner, to follow most of what Feynman is talking about, in any detail, in all but the non-technical lectures, just by listening to the tapes, particularly with regards to the mathematics, which is the heart of the subject. To follow along effectively one needs to simultaneously look at the photos of Feynman lecturing (not publicly available) with his demo equipment and blackboards, though looking at the corresponding chapters of FLP can serve the same purpose to a large extent, since most of the mathematics and figures on Feynman's blackboards are accurately represented in the books.
In my ~15 years of experience working with FLP, I haven't met a single person who has seriously attempted to learn physics by just listening to the FLP tapes. People who want to learn physics read the books, and those who are serious about it also work on physics exercises! People listen to the tapes because Feynman is a very entertaining lecturer even if you can't follow him when, for example, he is writing equations on the board, or pointing at one. (The sad truth is that many people also ignore the math when they are reading the books, so for them, at least, this is not much of a drawback!)