Sandy,
I would imagine that compared to Jobo or other rotary processing there is probably nothing to be gained by brush development (provided the flow patterns in the tube are consistant). However in comparing brush development to conventional tray development there is a noticable gain in evenness. The other thing that I have noticed is less potential negative damage.

Aside from that there is the benefit of standing in complete darkness repetetively moving the brush across the negative for extended periods of time and contemplating one's naval...something almost spiritual about it.