Aero Music adds the following features:
- Multiple on-the-fly playlists
- EQ Editor with preset names
- Mini queue (select the next track to be played)
- LRC and TXT lyrics support (yeah, I know, the J3 has native LRC support for some weeks, but I heard it sucks)
- Horizontal music UI (replaces Cowon's crappy coverflow; el maco's flow browser is supported, so you get a better coverflow implementation)
- Access to all music-related options
- Maybe other stuff I forgot to mention
Lynx adds the following features:
- Event Manager
- Custom icons (links to third-party applications on the mainmenu, such as Flash games)
- Folders (similar to the iOS 4 folder feature)
- Widgets (better widgets than Cowon's ones)
- Autoplay of Music on startup
- Security (Android-like pattern, password, auto-lock after 5 wrong inputs)
- PlugIn support so third-party developers can add more features
- Access to features like brightness, sleep timer, bluetooth,...
- Maybe other stuff I forgot to mention