Though i'm a fan of Fist of the North Star, and i have read all the chapters of original Manga...
Fist of the North Star characters are not as strong as DBZ characters, from the rational point of view.
I mean, they can destroy planets. That means their bodies are more hard than planets.
For Kenshiro to punch a pressure point, he needs the strength to do so, and he needs to use his touki to use it as attack power. DBZ characters are too strong for that.
Dude, i love FotNS, but just because their characters are weaker than DBZ characters, doesn't make them bad.