I agree with you stabman. I'm not sure what kind of training stvpourciau does, but they both can get you cut good. Except bigger knives have longer reach and can stab in deeper. Doesn't sound less intimidating to me. That is if your not fighting dumb downed opponents for drills or demos. I think you can have some murderous intent with any size sharp object for that matter.Bad idea.
Dangerous assumptions.
And, most importantly, what happens in a martial arts demonstration is not grounds for basing your approach to real life.
But if your not used to prison stabbings, a large knife can be pretty intimidating I think.