> I'm no audiophile, but even when downloading the highest quality files and playing them locally Spotify is still noticeably worse quality than the default AAC

> I'm no audiophile, but even when downloading the highest quality files and playing them locally Spotify is still noticeably worse quality than the default AAC files that Apple Music downloads for me on my purchased music. That's simply impossible, the Spotify client does not change your local files, it simply plays through your OS audio stack. You are noticing the difference in loudness, you can't know if the files you downloaded have been mastered the same way than the ones Apple Music is playing. I just tried with some of my own music, played the exactly same file as a WAV rendered from my DAW and then a very high bitrate export through the Spotify client as a local file, there's absolutely no difference.