In my humble opinion as to carry or not a defensive knife I´ve come to this: Althrough I´d rather be miles away from a knife fight, someday you will be assaulted by someone. In that case, training or no training, if you can´t run away, I think a one hand opening folder beats my fingernails.
I always have with me a Carson designed CRKT M21- 14 SFG semi serrated folder.
Regards, Ray