Here's a list of what I've observed in the Volt's USB music playing that's better than the Model S:
- The song played upon exit of the vehicle is remembered in terms of the location in the USB as well as the exact time in the song
- Embedded album art always displays
- No skipping when playing WMA files
- Song names display better. I'll have to look into this closer since I'm having trouble pinpointing exactly why i like the way the Volt displays the song name better.
- Loading of the USB contents is much faster (I've got a 32GB stick). I didn't even notice the load time in the Volt but in the Model S I've seen it take tens of seconds.
- Playlist support is shown but i haven't explored this feature
- Several more options I need to explore
Both vehicles allow you to search through the USB based on Albums, Artists, Folder structure. The music UI of the Volt leaves something to be desired but the consistent performance and multiple features makes me like it better. Hopefully Tesla can upgrade its music player.
I didn't upgrade the Model S to version 7 so i can't speak to any music player upgrades that version might have.