Intruder; personally I don't and I suggest that the entire comparison is a pointless red herring. Please read my earlier and, I believe, pertinent question at Srl 51. How easy/possible is it to detect the effects of seemingly minor damage in composite fabrications?
Taking it to the simplistic, we all know that "used" motor bike crash helmets are supposed to be consigned to the gash bin as they are only likely to protect you the once, even if they look only scratched.