The amount of condensation you get in the tank over the winter is a function of three variables: volume of air in the tank, amount of water vapor held in the air, and the % drop in temperature.
The ability of air to hold moisture is a function of temperature. The colder the air is, the less it can hold.
The metal tank is a problem as others mentioned due to rust. Yes, a metal tank will cool of faster, but at the end of the day once the tank & air inside reach equilibrium with the ambient temperature, the total amount of condensation is driven by the size of the temperature drop.