1/8 PVC Board
Regular Big Check material is a sturdy 1/8" PVC Board that is waterproof. It is very rigid and that makes it easier to hold between two people. It also gives the most professional, flat finish to print on.
My experience with the 1/8" Smooth PVC Board has been a good one. I always recommend it for high quality prints that will be displayed in lobbies of trade shows. It's smoooth finish makes it the ideal choice for viewing at a close distance. The only issue I've ever had is dropping from 5 feet up directly on the corner chipped off about half an inch worth of material.