@cbuck1, Well, you almost understood my question, except for one thing: I wasn't asking whether flac is best or if there's one even better... I was asking whether there's one that's slightly worse! But only slightly.
Look, I know that WAV can be used to save them, but that just seems extreme and unnecessary. Extreme, in terms of file storage, which I guess is cheap nowadays, but still... I do not have a high-resolution system through my entire chain, and don't want to play that level of the tech game. I want to listen to music, generally while I'm doing other things, and sometimes, for critical listening. I'm a musician, I have a good ear for sound and balance and color, so I want it to be as good as possible. MP3s sound dead and flat to me, but native CDs, AACs, AIFFs, seem to sound fine, based on non-rigorous comparisons.
I'm wondering if a format like Ogg Vorbis (which I guess is now deprecated) or Opus (which kind of replaced it) would be the way to go? I'm not sure if it's supported everywhere. I'm looking for the files I end up with to be playable on Mac, on my iPhone, on my Volumio streaming system (running on Raspberry Pi) and Windows. So, something north of MP3 and south of WAV, that's pretty universal. Seems like FLAC would be it, but... we've come full circle.