CDs: FLAC v ALAC (v Digital Download)

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. 

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. 

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

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?

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

Years back, when I just started putting cd into hard drive, I did not know about any of that stuff. So most are in. aac, it’s ok, when I listen for effect, I pop in a cd and relax on the couch with a triple dram and a frozen piece of granite 

or fire up the old trusty SL-1200 mkii. 
I use the nightclub II concorde if the low end is low, the nightclub II has a great bass extension. The Arkiv concorde boosts the mids and treble for when I ,run my LPs’ into audiolab 3.0 ,clean them. Up a bit, and record them to nice taiyo yuden cdrs.  
 

Everything has been applelossless for several years now.
in my car don’t give a darn about sound, I only have the 2 lil speakers on the side panels , the others stopped working about 3 months after expiration of the abhorrent gmc service and overall garbage they sell. 
 

darn,,another rant, thanks for wasting 3 minutes of your life, you will never get it back 

What is your goal? A CD rip to FLAC or ALAC would be equivalent (both bit perfect). You can convert files between FLAC and ALAC format with no loss in quality.

Do you still have the CDs? From Qobuz you would have to purchase the download files.