I buy audiobooks from Libro.fm rather than Audible, primarily so that I can listen to the audio using the Overcast podcast app. Overcast is more familiar to me than the Audible app, and Overcast has excellent audio quality.

As a side-benefit, I also get non-DRMed audiobooks, which means I’m not locked into the Audible ecosystem. Also, I get to support a competitor to the Amazon monopoly. I buy plenty of stuff from Amazon, but it’s nice to occasionally shop elsewhere.