I have both Amazon HD and Qobuz streaming via Denon Heos link and a Firestick. First of all, Amazon sounds great. Firestick displays track quality, downstream device capability and playback sample rate and it does output the rate it says it does. I listen to mostly classical, jazz, acoustic and international stuff. My observations:
Amazon has a bigger selection to choose from. It always sounds fuller with more punch than Qobuz. Qobuz sounds a bit more open and resolving in many instances but is definitely a bit lighter and brighter even compared to my Wav or Flac files.
Many Amazon releases seem to have additional processing for their 3D tracks and sound different from the originals. In some cases that is a welcome change but not always. The DG releases on Amazon sound better than what they released on CD, You fans of classical will want to get it just for that reason.
I find myself streaming much more than playing SaCD and CD these days. People who complain of a big difference in SQ have not set it up right.