Poly: cheap, insulated, light, non recyclable, short life, blows away in strong winds, can't be "flamed", damaged by hive tools,
Cedar: expensive, lighter than pine, long lasting
Pine: cheaper than cedar, heavier than cedar and not as long lasting
Wood can be flamed and recycled and also looks nicer.
You pays your money and takes your choice. I have used all three and even plywood. For looks cedar is always going to be best so if you have deep pockets buy good quality cedar.
Because of its insulating properties, poly is probably best for Nationals and other single walled hives but with WBCs the insulation can go between the lifts and boxes so they can be made of decent wood for the lifts and plywood for the boxes. Since they are often painted, pine will do although the lifts are heavier.