The primary difference between a trilby and a Borsalino lies in their design and origin. While both are stylish hats, a trilby hat women often choose has a narrower brim that's turned upwards at the back. Borsalino, on the other hand, is a brand known for producing a wide range of hats, including fedoras, which typically have a wider brim than trilbys. It's worth noting that while many might refer to a wide-brimmed hat as a Borsalino due to the brand's popularity, it's more about the style and less about the specific trilby hat womens fashion choices.