I know you are specifically asking about apple vs amazon but if you ever want to try something different you may want to do a Deezer trial. Huge library and good interface IMO. I switched from Tidal to Deezer.
Apple vs Amazon
I'm not fully committed to streaming yet. DAC is low end. Finishing a 3 month free Apple Music trial. In truth, it doesn't sound that bad to me but tonight I started a 3 month Amazon Music trial and just after spending about an hour with it, it seems to sound better than Apple Music running through the exact same system. Fuller. Richer. More precise bass. No A/B testing, just a general impression. It might even be the music selection. I don't know. Is there any actual reason for this to be true? Or is it just me?