Tidal vs Spotify there is no comparison, Tidal is a Premium streaming service if your after good quality files, but does not have the mass amount of music files and different genres that Spotify has, its most DJs dream to have spotify integration with Serato, especially with mobile djs, I think it will happen in future but not at the moment something to do with licensing,

but feel free to add to the multiple requests members have submitted in the future request section here :serato.com

How about Amazon Music Unlimited?
Has 50+ million songs!!!