Resilience : the ability of a material to return to its original shape when you stop using it. Clearly, a carbon fiber fin will provide a much better performance because it returns more energy (10 to 15% more) than a fiberglass fin. For the same physical effort, it will allow a more efficient movement.
Strength: Both materials are very resistant to bending and twisting. Fins can be scratched easily but this does not affect their performance at all. Carbon or glass, they can break if you lean on the fin while it is blocked.
Durability : a draw. Both fins will keep all their qualities for many years. On the other hand, neither of them like to stay in the sun for a long time nor to be trampled on a pontoon!
The price : advantage fiberglass which is less expensive than a carbon fiber fin.
Weight : never neglect it if you have to go out or train for several hours or if you have to take a plane... The advantage of a carbon fin is that it is lighter than a fiberglass fin. But be careful, what makes the weight of the fin, it is especially the shoe!