Aiff or Flac

When I ripped all my discs, I ripped some files to both FLAC and AIFF to compare. 

Granted, I compared with headphones on my Apple laptop computer, but there was additional background noise on all the FLAC files.

I determined that whatever additional computer resources that convert the FLAC files on the computer added additional noise.

I don't know if this would transfer over to decoding on audio equipment but I decided to rip to AIFF and avoid the possibility.

However, listening to FLAC files on Qobuz through my audio gear sounds great. I still wouldn't change my decision after my test, though. There's no gear that I own that can't play AIFF files. 

I use flac and everything sounds beautiful

I’m also a FLAC user. I compared FLAC rips directly to the original CDs before settling on FLAC for my music storage and was unable to tell a difference.

However, as someone else previously noted, while lossless, FLAC does involve file size compression in a manner similar to Zip files, though FLAC is specifically for music. FLAC assumes that your hardware is adequate for doing the decompression. Most modern equipment should be more than capable for this task but I suppose there might still be some gear out there that isn’t up to snuff.

There are two reasons to use FLAC: saving storage space and adding/editing metadata. Since storage is cheap and ripping software such as dBPoweramp handle metadata for aiff/wav there really is no advantage to flac unless it sounds better on your system.

I worry that a lot of audio myth here was formed with older DAC's.  Modern DACs, even the cheap ones, have amazingly good clocks.

Definitely worth listening for yourself.