There are several comparisons online but with all streaming quality settings on max, there’s very little to choose - some reviewers said some songs sounded better on Spotify and others sounded better on iTunes.
I tried Tidal for a while and it sounded great but twice the price and as my Hifi amp has Spotify connect that just makes more sense - I also find Spotify’s algorithm recommends me music more accurately than the others.
Apparently Spotify are bringing out a ‘lossless’ type service to compete with Tidal soon, too.