Martial Arts is a crapshoot. I seen plenty of Karate guys get their asses handed to them by some street thug. Same goes true with knife fighting.
If you go to a class and the guy starts off with a reverse knife hold and does flowing slashing motions, you should offically be able to smack him in the mouth and walk out of the class. That crap will get you killed.
It should be fast stabbing and slashing with a short blade. Think like fencing or a prison shiv attack. A longer blade like a Ka-bar on up will be better at slashing and chopping of flesh.
No ghey flowing martial arts katas. Pulling a knife is serious business and like a gun should only be if your life is in danger and you need to kill someone. You can slash you way out of bad situation for a "possible" less then lethal option and getting jump buy multiple attackers, but all in all, you pull a knife your main goal is stabbing and slashing the bad guys vitals as quick as possible.