iOS/Android: Spotify works great for music sharing and third-party plugins. Apple Music works great for offline play. So I juggle both. It feels a bit like shared custody, but it’s a lot easier thanks to the mobile apps SongShift and Stamp, which efficiently move playlists from one service to the other.
For iPhone users, SongShift is your best bet. It has a clean, self-explanatory interface, and it’s just $5.99 for unlimited use (free to try). It works with Spotify, Apple Music, Tidal, YouTube, Deezer, Discogs, last.fm, Hype Machine, Napster (lol) and Pandora. It saves your past playlist exports and gives you the option to keep playlists synchronised between services.
If you use an Android, Google Play Music or Amazon Music, use Stamp instead. It’s slower and clunkier, it doesn’t save past exports, and it costs $US10 ($14). But it covers more services: Google and Amazon, plus Spotify, Apple Music, Tidal, YouTube and Pandora. There’s an equally clunky Stamp desktop app, which works with Spotify, Google, Amazon, Tidal and Pandora (and imports from, but doesn’t export to, Apple Music).
On iOS, both SongShift and STAMP only work while the app is open. Both apps list which tracks successfully transferred, and which failed. Both work great for a one-time library transfer, and SongShift works great for juggling two services longterm.