Carbon fiber shells are incredibly strong and noticeably lighter than other materials, which is why they're popular with racers who count every gram. If you're competing or simply prioritize having the lightest helmet possible, carbon fiber delivers on that promise.
However, for most recreational skiers and snowboarders, the weight savings won't meaningfully improve your day on the mountain. A polycarbonate helmet is already quite light and offers plenty of durability for typical resort riding. You're paying a significant premium for carbon fiber, and that money might be better spent on other features like better ventilation or a MIPS rotational impact system.
Also keep in mind that shell material doesn't equal safety level — all certified ski helmets meet the same impact standards regardless of whether the shell is carbon fiber, polycarbonate, or ABS plastic. The shell material affects weight and durability, not the helmet's ability to protect your head in a crash.