As long as you can delete them without being forced to listen to them first, I don't see there's much of a difference to be honest
Actually, I think the audio messages may be an improvement in this respect. As a compulsive reader, I find it difficult to avoid reading at least the beginnings of textual messages on LI.
(I used to find some interesting content in LI group messages and blog posts, but one of their UI changes made it extremely annoying to read anything on the site. If memory serves, they broke keyboard scrolling by having some idiotic "do you want to post a message?" dialog pop up over the text if you pressed a key. Idiots.)