Brake problem - got two different diagnoses from two mechanics?

At low speeds (40 and under) when I'm braking, occasionally my brakes will suddenly disengage for a second, causing me to pick back up some speed, then re-engage. One mechanic said my hub embly has metal shavings that are messing with the ABS sensor and causing the problem. Another says it's the rotors being uneven. Any thoughts? I'd like to avoid going to a third mechanic. Thanks.