I spent quite a few hours comparing carefully. Qobuz to Tidal to SACD and CD when I had all 4 to compare.
I can clearly hear the difference between Qobuz and Tidal MQA. I do not have an MQA dac to do the final unfold and as such the resolution drops to 13 bits from what I understand. That's how MQA works. But it is not the "resolution" difference I hear.
It is a hardness of tone, a bit of glare and artificial edginess that is there which is not present on Qobuz.
MQA is a lossy not lossless process with their own trickery of the files. I can hear it and I don't like it. Perhaps if I had an MQA dac I may feel different if there is a difference in the final unfold. As it stands right now, I avoid Tidal MQA and go for the Qobuz version which is almost always a choice for me.
Qobuz to CD to SACD comparison. With the higher resolution and often even the 44.1 files are either identical or I had to really struggle to hear any difference. My best SACD sound identical to Qobuz to my ears.
My streamer is the Bryston BDP-Pi and I used Luxman D-06u for those careful comparisons but they had just as audible and repeatable end result over my headphone listening station at the computer. With a nice dac, SS and Tubes. The dac once again is not MQA either.
In conclusion. To my ears, I strongly prefer Qobuz and I have zero hesitation streaming for my whole listening experience and not spend money on physical media.
As always, YMMV and all that stuff...