BB-5s suck, IMHO. I bought one and it was so pitiful I refused to put it on my bike; so I put a used BB-7 on instead. 7s have about twice the pad surface area but in my experience they still require constant tweaking. A step up from that is the Tektro Spyre/Spyke. On those, both pads move, making for much better operation and almost eliminating rotor warping issues, as well as requiring a lot less fussing. Hydraulics are still better -- more powerful, operate more smoothly, and once they're set up they require very little in the way of adjustments. Even a low end hydraulic will be better than a mech.