I can nit pick and come up with differences in the SQ of Tidal and Qobuz (and if I do Qobuz does come out on top... in my system), but the reality of it all is that both provide very credible sound and either one is certainly good enough to allow you to sit down and enjoy the music.
But for me streaming is not about replacing my other sources of music , but rather expand on them. I use streaming service not as a primary source, but as a way to preview things I might purchase or give me instant access to something that I do not currently have in my library that I want to listen to at that particular moment.
So for me there are two things that are much more important than sound quality when looking at the two service. First, how well does their service integrate with the hardware and software you use for streaming in your system. For a streaming service to be useful it must work easily and seamlessly with your system, otherwise it will end up frustrating you and over time you will just stop using it. One example that comes to mind is that Amazon Music does not work with Roon and according to Roon in spite of their trying to make that happen, Amazon simply has no desire to make their service Roon compatible. In my case this this makes Amazon Music a non-starter for me. Secondly, and I think most importantly is the fact that these service have different selection criteria when it comes to deciding what music they should carry. You need to take a look at what each of then keeps in their collections and pick the one that most closely matches your music preference so you can get the most out of a subscription. Because let's face it, a music service that carry the kinds of music you like to listen to will not do you much good.
So in my mind the sound quality of both systems is good enough that it should take a back seat in the decision making process and you should choose the service that most easily makes it possible to find and play the music that you want to hear. because in the end, these services are not streaming you sound quality, they are streaming you music and therefore you should let the music guide you to which one is best for your system and musical tastes.
