That's part of it too, but superbits always have DTS, which takes up an enormous amount of room, compared to regular sound tracks. So the combination of a higher bit rate, and the DTS track, pretty much leave no room for anything else. I'd rather have a slightly lower bit rate, Dolby sound (since in tests there is very little difference), and a ton of extras.
MTFBWY and HH!!
Jar Jar Binks