Personally, I like Slacker the best. In fact, my car was just in service for 3 weeks and had to drive my '94 Camaro. I preferred to Bluetooth Slacker to it while driving... Great channels, the DJ's are good without being too much, and the song selection is excellent. If I don't like a song, I just forward past it. That's the great part about the Tesla account... unlimited skipping.
I also pay for Tidal (not sure why, but I like the Master music sometimes), and also pay for Apple Music (my teenagers prefer it). I've tried to like both radio options, but to no avail. Years ago I paid for Deezer, Spotify, and Beats/Mog. Honestly I think for radio function, Slacker is the best. True, you cannot select your songs, but that's why I use other ones for that.
It would be best for Tesla to create an app plugin similar to Sonos whereby we could select any streaming services we prefer.