These were my impressions of Qobuz vs Amazon HD as of Nov 2020:
Winner for me is Qobuz for the following reasons.
Amazon: Sounds more flat. Less drive than Qobuz so that some music sounds like it is plodding along. Sound is less full. Amazon HD doesn't necessarily do anything wrong (as does Tidal), but also clearly not as good as Qobuz to my ears.
Qobuz: Much more presence than Amazon HD. More 3-dimensional. Better pace and drive. Better low-frequency response & definition. More range to conveying the emotion in music: (i.e., calmer for calmer music & more drive & pace for more upbeat music)