The audible subscription is a much better value, when I get full on credits I can just cancel my sub until I'm ready for more books and don't have to pay $40 or something. If I really want a cheap book (something less than the subscription price, I will just buy outright and save my tokens for something expensive)
My only real complaint with Amazon (and it may be a publisher rule) is you don't get the kindle version for free. If I want to switch between book and text seamlessly I have to buy both versions.
Does anyone know if the author gets less money when buying an audio book vs a text book?