Why care? Because I can't afford them all and want to only pay for one streaming service. But if you are right (and you probably are) and they are all close, then maybe it's more about the user interface.
I'm not really asking here "Which is better?" what I am asking is "How do you, personally compare music reproduction?" I'm interested in other people's methods and perceptions.
Presumably everyone does this prior to settling on the equipment that they "just listen to music" on, so there must be some kind of analysis involved.
One thing I have noticed is that if the reproduction is "better", I can usually hear the background vocals and harmonies more clearly. Being able to tell if a harmony is sung by a different male, female voice or just the main vocalist doubling up.
I find this thread very readable. Important aspects are discussed here that can contribute to a good experience of sound reproduction. And with a bit of luck, it goes beyond sound reproduction and opens the door to music.
I would like to go back to the specific question of the thread starter Wulbert and because the topic here is so important and fundamental, it expands very quickly to all kinds of aspects that I think Wulbert did not necessarily want to discuss in his specific question.
Let's assume that you, Wulbert, have a nice hi-fi system and that you know all the issues around objective vs. subjective criteria, that you are aware of the difference between someone paying attention to music or to the sound characteristics of their equipment or their room. And also what influence sound characteristics can have on the willingness to immerse oneself emotionally in the music and/or to "read" the music (not the equipment) "critically" with one's ears.
Based on this, I understood the question as how one can best judge the sound quality of different streaming services. This can be done on an "objective" level but also on an emotional level: are there differences in the streamed music of different services that make me like listening to them more or less?
My 2 cent. First of all, I don't want to compare streaming with other sources like CD players or vinyl. It is challenging enough when we consider that the streaming quality also depends on the device used. Whereas 30 and 20 years ago I bought quite high quality equipment which I still use, mostly alternating at intervals of a whole year (Mcintosh and Quad amps, Tannoy Canterbury, Quad ESL57, Klipsch LaScala, Meridian CD player) I am so far satisfied with a less expensive streamer. I don't spend a lot of money on digital equipment because every three years it's no longer state of the art. Sure, a Meridian or Linn streamer might sound better, I never heard it but I'm happy with a Bluesound Node after having Sonos and Node 2i before. Yes, I am really happy with this device and its sound. If I want it to be really nice, I put on a vinyl record anyway but a streamer is so useful also the many radio stations where „tunein“ comes free with the Node without interruption by ads.
Now to my impressions of the streaming services. First of all, a tip for the thread starter: you can cancel most services after a short time or even try them out for free for four weeks. I would make use of this to enable my own impressions and comparisons.
I have decided to use Tidal. My Bluesound Node streamer can play MQA and I can clearly hear the difference to CD quality. It's not about "sound" for me. It's about the music having more drama, inner tension, timing and dynamics as an MQA recording. The MQA version penetrates directly deeper into my emotional experience (when comparing with the "CD" quality really please always use the same recording with the same mix, the deviations of the sound can be striking, and I have never heard until today that I like a so-called remastering better than the original recording, but that is another topic).
But even at the level of "CD" quality, I strongly prefer Tidal. My adult kids use Spotify because there are "cooler" playlists made for young people. So I have this comparison. The difference in sound compared to CD quality (we are not even talking about MQA) is immediately audible, noticeable, tangible. An example, on the recording of the piece "Interplay" by Bill Evans from 1962 with Jim Hall (only in CD quality in this case, but already good) Bill plays in his solo single long notes in the soprano range of the keyboard. This can be heard very well e.g. at minute 4:16. The piano is not tuned sterile and you can hear a wonderful very slight chorus effect of the three piano strings of the single note. I don't hear that on Spotify, there it's more just a note that doesn't float. But that's just my two cents.