What is the difference between a PVC and PET defogging film, and does it matter for standard bathroom use?

Both PVC and PET films function on the same resistive heating principle. The practical difference lies in long-term durability. PVC has a lower heat deflection temperature and is more susceptible to dimensional deformation under repeated thermal cycling — the daily heat-up and cool-down cycle every bathroom mirror undergoes. PET maintains its structural integrity under these conditions significantly longer. For standard residential use, either may suffice. For commercial installations, hospitality environments, or any application with a multi-year performance expectation, PET is the appropriate specification.