Both have their pros and cons. For one, Polyester is much more breathable than Silicone. On the other hand, Silicone is much tighter when it comes to grip compared to Polyester. Choose according to your taste and needs. Consider where you want to use the gloves and what environment you are in. Some gloves both have Silicone and Polyester materials in their fabrics so choosing between these two is not that much of a deal.