There are two compounding factors

• heat capacity: any short term experiment will measure heat capacity first, conduction second

• locality of contact: contact along the whole length of the straw eliminates heat conduction along the length of the straw. A single point of contact (holding the straw with fingers instead of the whole hand) behaves differently.

I thought plastic straws were thinner than 0.2 mm, so maybe the metal is actually better.

It's fun arguing about these technicalities though!