Spotify Premium vs Tidal ... opinions?

Tidal is better than Spotify. The HiFi subscription is CD Lossless, and it costs the same as Spotify Premium, which is lossy. Spotify Hifi is not out yet, delayed due to licensing issues, so no one knows yet about that.

For Tidal, their HiFi Plus subscription is controversial. It uses MQA which is not lossless, making Tidal not a great option if you want high res (higher resolution than CD), for that, consider Qobuz. What MQA does offer is high res that is much smaller file size compared to similar resolution flac files, while being vastly higher quality than MP3. It's a weird trade off considering the audience and the fact that bandwidth is generally not an issue.

For CD Lossless, Qobuz and Tidal are pretty much rivals, many people buy both and use Roon to manage playlists, this will maximize quality and track availability. I just use Tidal and then buy CD's of what's not on it and rip them myself to flac for network streaming.