The answer is: flexibility. Roon works perfectly out of the box if you just want to plug'n'play. But it allows endless customization without interfering to my files and offers tons of features:
- It has a huge music database. It will link albums, artists, performances and other. But it is one click to use own tags. If I want to override particular tag - piece of cake. Roon will store it in the local database without spoiling my files
- Volume normalization makes wonders to playlists composed of new and old recordings. Again, Roon can use own data for it or my tags
- Working with zones is super-easy
- Parametric EQ is unmatched and can be set separately per each zone
- Crossfeed!
- Artists bios, live lyrics and other cool stuff
- Focus offers brilliant music library filtering
- Activity summary
- Live radio when I am bored with own music library
- GUI is more than ok, but was better in 1.6 IMHO
- Brilliant playlist management - Roon can show in album view if a particular song is added to a playlist
- Migration of Core between PCs is a piece of cake. Normally I run Core on Intel NUC. Before longer travels I just copy music to USB stick, create backup, load in on my MacBook and done. Migration between different OS is seamless
- No lags, dropouts, etc
- It manages flawlessly multiple versions of the same album
- It uses tags to organize library instead of folders structure which allows to avoid a lot of bugs present in DLNA solutions