Cadence readings Source: Dedicated Cadence Sensor or Vector 3 cadence values ?

Hello

Is there any advantage of installing a dedicated Cadence Sensor or are the V3 Pedals signal a reliable Cadence source ?

If a dedicated sensor is installed, will the power value be calculated with the dedicated cadence sensor or with the pedals readings, or will it depend what Cadence source is paired with the head unit being used ?

Thanks

Gias10