First off you gotta remember that the BP-8 was a first generation mulitefx, 5 or so years before the other units you are comparing it to. The newer ones have features, editing functions and sounds that the BP-8 does not have.
OTOH the quality of the BP-8 is of a much higher level, much more useful for a discriminating bass player. IMO it is more real than the simulated or modelled tones in the newer boxes. The Preamp has many of the characteristics of fine tube preamps with more depth and some of the warmth of a real tube. The EQ works like you'd expect. The effects section; flange, chorus, phase, envelope and octaver; have a more analog or box quality(that's a good thing), but you can only use one of these at a given time. The delay and reverbs are of a high quality studio level not the "also included" quality in most contemporary multiefx units.
Don't get me wrong I don't hate multiefx units, I have several Zoom units that get daily use, but the BP-8 gets used for studio recording and more high level work.