When I used Spotify I moved to Tidal and recently moved to Qobuz when it arrived in the US. Between Spotify and Tidal, Tidal sounded better on my system, my room, with my ears. At the time I ran ND5 XS then a NDX with a SN2. Today I have a NDX 2 with the SN2 and prefer the sound of Qobuz.
If you don’t see the offer I would email TIDAL and tell them you are interested and ask them what the best deal they can offer for you to switch. It never hurts to ask and you may end up with a better deal then you expected.
Purely on sound quality, I thought that the 320kbps Tidal was much better. The Spotify catalogue is broader though, so it depends where your tastes lie. The main decider for me was the Tidal/ Roon integration. I am listening to a lot more music now, and have sprung for the lossless version of Tidal since subscribing to Roon.