Mr. Sawyer?? Who's that...
The reason The Klemheist works with fewer wraps, I THINK, is that the wraps tighten up in one direction only, thus making the knot effective with half the wraps of a prussik.
I've done prussik's to zing-it. It just takes 4 wraps, and like others said above, it works best with a smaller line wrapped on a larger one... I find wrapping prussiks more than 2-3 times to be hard... but it's probably my fat fingers and failing eyesight.