There is some difference.
Posts in BW should ideally be from people [not musicians, maybe event/gig organisers, wedding etc] who want bands.
Posts in MA should ideally be from musician/s who are free and available to either join existing projects or form a new group.
One way to make things clearer is to take a cue from relationship classified ad listings - Men seeking women, women seeking man, etc - and rename those forum sections using the same structure.
Then, we would have:
- Musicians seeking bands
- Bands seeking musicians
We might have to add another if necessary to cater for non-musos:
maybe - Organisers seeking musicians/bands.
But anyway, I think things are working pretty okay as they are, majority of the posters do know which goes where.