CDs: FLAC v ALAC (v Digital Download)

 I _think_ ALAC is a little better in terms of compression.  So long as your player supports both there is no reason to convert.

I remember reading discussions a few years ago. A few thought there was a minute improvement using Flac over Alac when ripping CDs.

I'm guessing no difference using my CDs over the same pressing from Qobuz?

It’s been a while since I had ripped to iTunes but I remember reading about and then making my own comparison between ALAC and FLAC.  As @erik_squires says there was supposedly some minute improvement with ALAC but it wasn’t audible imo.  I think the only reason to convert from ALAC to FLAC would be a concern that future players may not support ALAC

If there is any difference in playback quality it was claimed that it was in the different algorithms needed to decompress each. Either from:

• Noise generated by the CPU during decompression
• Different timings of decompression causing the buffer/clock circuits to behave differently

As a person who evaluates algorithms for a living, I’d say that IF this were true it would be very much something that would be implementation specific. There are several major variables at play. 

Everything that matters plays both formats, which are equivalent for all intents and purposes. ALAC is the Apple version of Flac, both free lossless formats playable on all modern equipment.