The same switch will always last longer when used to break the ground rather than the line (power) because there's less arcing and contact metal transfer. With that in mind a switch breaking the ground will NOT protect against accidental shorts to ground. Personally I think killing the power to a lift gate would be better, less problem with slush and snow,(slow drain on battery)and you don't have to worry about someone bumping into the rear and shorting out the power lead and burning up the truck.