How do porcupine fish spines differ from burrfish spines?

Within the family Diodontidae, the primary distinction between porcupine fish and burrfish lies in the mobility of their spines.12

• Porcupine fish (genus Diodon): These fish possess spines that typically lie flat against the body. The spines only become erect when the fish inflates itself as a defense mechanism.12
• Burrfish (genus Chilomycterus): These fish have spines that are permanently fixed in an erect position, regardless of whether the fish is inflated.12