ss urethane is preferred by many over bc/cc. simply because of appearance. in time the clear coat will get fine scratches in it which will give the car a cloudy look. light bouncing off the black under the clear. this does not show as much in ss . cutting and buffing is no different . both will give you the same quality .
depth is achieved by the clarity of the finish. not paint type or # of coats .
pigment has nothing to do with uv protection.