Any HDPE plastic pallet weighing 35kg requires 805 KwH of energy for production.
This is equivalent to 120kg of coal.

It takes about 1.76kg of petroleum to produce one kg of HDPE.  This steel pallet, the 25kg repeat use version, requires only 124 KwH of energy to produce by comparison.  This is equivalent to 18.6kg of coal and about 15% of that needed for HDPE.  Also the energy cost to recycle a badly damaged steel pallet is 15 KwH or about 12% of a new one. This is under 2% of the energy required for a new HDPE pallet.  Each steel pallet is infinitely recyclable for the same product without degreading material quality.

Recycling in decades to come will be even more energy efficient using the base stockpile than from new steel production. That is the BIG picture.

From a production perspective and an energy consumption basis steel is the clear (and green) winner over plastic by 85%.