Avid should have never released the BB-5. It took everything that sets the **real** Avid mechanical disc (previously referred to as the Avid Mech, or more formally the BBDB, but recently renamed the "BB7") AND DID AWAY WITH IT.
Well, OK, not everything. But the BB5 lost the outboard pad adjuster. So now instead of a simple two-click-and-you're-done pad adjustment, you've got to screw around with the barrel adjuster to effectively shorten the cable in order to adjust for wear. What gives?
Then they went and changed the pad design. Took a whole lot of years to get that compound just right -- I hope they stuck with that -- but now just about every shop you walk into is going to have Avid pads for the BB7 and prior models, but not yours.
But you've still got the CPS system that Promax doesn't have, the super simple system of convex and concave washers that make alignment a cinch. And, for whatever it's worth, you've still got Avid's good name (truth be told, that was worth a whole lot more a couple years back in their pre-SRAM days, when good customer service meant customer-accessible telephone parts support).
Anyway, the BB5 is just Avid's way of capitalizing on their good reputation with a dumbed down, less expensive version of the industry's flagship cable operated disc brake. Nothing special there.