I recently started a trial of amazon HD music to compare to spotify premium that I have been using. I am using HEOS for amazon and connect for spotify both through my Denon X3700. I think I might be able to hear a difference but it is very small in my normal listening. I am looking for suggestion on music that might showcase a bigger difference between the service to help decide if switching is worth it.
I don't have anyway to level match the sources so this might all be moot anyway.
Studies have definitely shown that it's possible to discriminate lossily compressed recordings from their lossless originals, although at 320kbps it tends to be very difficult, and to take some training, the right source material, and a good system. So I wouldn't expect there to be any audible difference between the two for most recordings/systems/listeners, although subtle differences may be apparent in some circumstances.
Also keep in mind that a lot of streamed content from major labels appears to be
watermarked, which may result in audible quality degradation regardless whether the content is streamed at lossy 16/44 or lossless 24/96.
Personally, as I started with Spotify before a lossless hi-res service with a significant collection of music existed, I have decided to stick with it. I guess there might be some subtle audible differences, but having done a number of 320kbps to lossless blind tests on myself, I've concluded that in most cases I can't hear differences, and in those few cases where I might be able to, the effects of lossy compression are very subtle and don't hinder my enjoyment of the music, anyway.