“Save to new playlists” will save whatever playlists you’ve selected to new playlists, including your “Liked Songs” and “Liked Albums”. Or in other words:
- Playlists -> Playlists (with same names)
- “Liked Songs” -> a “Liked Songs” Playlist
- “Liked Albums” -> a “Liked Albums” Playlist
If you are not 100% familiar with Apple Music then choose this option – it is simplest to understand, and if you want to move the tracks in a playlist to your library at a later time it’s easy to do in the Music app.
“Save to your library ‘as is’” will save Playlists as Playlists but will transfer Liked Songs & Albums (if selected) direct to your library. Or in other words:
- Playlists -> Playlists (with same names)
- “Liked Songs” -> the “Songs” section of your library
- “Liked Albums” -> the “Albums” section of your library
This will copy your Spotify library (for example) over to Apple Music in the way which is closest to how you see things in Spotify.