Stabbing is the least effective technique for self defense. Unfortunately, situations of real self defense should involve defensive strikes/slashing to the eyes, neck, arms, groin and bowels.
At the risk of sounding like a mall ninja deluxe lol...
My Father actually used to train the British police in self defense way back in the 60's. He always taught me to run from a knife fight, but he also taught me a little about knife fighting.
Stabbing is a far more lethal wound then slashing can be. It might not kill you instantly but you run into the problem of bleeding internally. Stab wounds to the stomach especially are dangerous as it's soft and takes a long time to heal.
Now my Dad taught me blocks from knives that are trying to use slashing, and if someone is trying to slash at you I think it is possible for a well seasoned martial artist to stop that. But I'm here to tell you that 99% of those techniques are total bunk. The reality is most of the time your going to be assaulted in a "Prison style Shanking" and no martial arts technique can really stop it. All you can do is put your arms in the way and hopefully they hit your arms and not your internal organs.
Another thing people don't understand is just like a police officer you need quite a bit of distance between you and your assailant to draw your weapon. I think a fixed blade knife that has a modern sheath that holds it in place without a loop or lock would be your best bet. But again that's if you see it coming.
The other thing and the most important thing is you need the mindset to actually use your weapon, and that takes training. Even though I was taught all this stuff I don't have the mind set to actually use it. I've never once in my adult life have been in a fight. I would hesitate as all I would be thinking about not wanting to be arrested and spend the rest of my life in jail, and that hesitation would get me killed. Not everyone has it in them to want to hurt another person.
If someone mugs you with a knife just give it to them. The $100 bucks you are risking your life over just isn't worth it. Heck in America the trip to emergency will end up costing way more then $100.
EDIT: Sorry just also wanted to ad. IMHO It doesn't take a knife. You can gouge someones eyes with your fingers, and kick someones groin. If you you use a knife in SD it's a lethal last resort.