I don't know quite as much about the other models ( L and M 100 ), but I do know for sure that the B3 and C3 had the exact same internal components. The thing that set them apart was the cabinets themselves. You can read about this on one of the Hammond websites.

I wasn't aware of this when I was listening to ELP in their heyday, hence the C3, as Emerson used it, became my personal favorite, mainly because I favored his playing techniques and his soundset. Keith Emerson used the 100 series boards, (along with just about everything else under the sun ) but in interviews he has noted that the C3 is also one of his favorites.

AJ