Thomas,
This depends on what do you mind speaking about self-defense.
If you are in the situation when the single life saving solution is to cut your assailant Vesuvius is as good as each other knife. There are at least few dozens of points on human body where you can deal dangerous or even deadly wound even with half shorter blade. Honestly wish you never to find yourself in such conditions, greatly probably you will not be too happy even if you will win this fight and escape from danger completely unharmed...
On the other hand if self-defense should depend on showing your assailant your knife and such way convince him (them) to let you alone... Hmm, this depends on your opponent(s) intellectual condition. Sensible man would really let you alone, the problem is that sensible men usually do not harass anyone causing them to defend themselves with knives.
However you have much less chances to scare your opponent(s) with Vesuvius if you deal with idiot(s)...
