Choosing the material of a game card holder usually comes down to your needs and personal preference. Here are some common game card sleeve materials and their characteristics:
 

Polyvinyl chloride (PVC): PVC is one of the most common materials for game card sleeves. It has the characteristics of high transparency, good flexibility and strong durability, and can effectively protect the card from scratches, bending or damage. PVC card holders are usually relatively inexpensive, making them an affordable option.
Polypropylene (PP): PP is also a common material for game card holders. It is more environmentally friendly than PVC and does not contain chlorine, so it is also considered a safer option. PP card sleeves have high transparency, good durability and high rigidity, which can provide better card protection. It may cost slightly more than a PVC card holder.