I may be soundly refuted by the experts on this, but here's my take on the sound. Like every banjo, each long-neck has it own individual sound, some twangy, some bright, some brassy, some tinny.

The difference is that you can go to a lower key in the open tuning. That is, instead of the standard open G tuning, you are actually in E or F (I think) and have to capo up those extra frets to get up to the standard G of other banjos.

Therefore the sound difference is that of being able to play "open" strings/chord postions in a lower key - plus the individual characteristics of the banjo itself.