What sounds better is purely subjective to one's personal taste and associated gear. Since you're listening through Sonos, there shouldn't be any discerning differences between Tidal and Deezer Elite. They both stream music in 1,411Kbit/s FLAC format on Sonos.
If anything, Deezer Elite should be less expensive than Tidal ($19.99 per mo.).
I am not sure about the content with Deezer as they started out with pretty limited library. You can always sign up for a Tidal free trial and compare the content and streaming quality. I switched to Tidal from Rhapsody and Spotify last year and been very happy with Tidal high quality streaming.