On a double gun a single trigger must momentarily disengage from battery, or possibility exists of both barrels firing nearly similtaneously. The human brain unknowingly pulls the trigger during recoil. Both inertia and mechanical single triggers accomplish the same thing. As for the supposed advantage of the mechanical trigger allowing the second barrel to fire in case of a dud, I've never had the situation come up in 23 years of hunting, probably never will.

-Shoot Straight, IM