First, a video, for demonstration purposes of stabbing working better than slashing against armor. We'll be looking at knives in particular, because I said so and am presently too tired to make the words work to explain why. Mostly because no matter the tech level, any character I build will probably have a knife, if not be an actual knife fighter.
By GURPS rules, all damage is the same, whether it's concentrated to a point or spread over an edge.
Now, to analyze the video. Those are very clearly all-out-attacks (strong, +2 damage), combined with reversed grip (+1 thrust damage). At ST 10 or higher, that +1 still isn't enough to put it on par in terms of damage with a swing, unless weapon damage modifies it.
Large Knives, without alternate grips, do Thrust impaling damage on a stab or Swing-2 on a cut, which puts the base damage output equal with either type for a ST 10 or ST 11 fighter. Beyond that, however, and the gap begins to widen substantially. At ST 13, a large knife will do 1d of damage thrusting, but 2d-3 of cutting damage; while both average rolls are the same, a good hit with a swing will do substantially more damage, 9 vs 6. The gap quickly widens from there, as swing damage improves at a much faster rate than thrust.
So, the rules say that against an armored opponent, you're better off hacking at them than using a pointy tip to try to get through. How do we fix this?
My first inclination involves reversed grip. On something like a knife, which can be swung much more handily than any larger weapon when reversed, change damage on impaling attacks to +1 Imp or Swing Imp, whichever is better, and implement Pick rules. In strong hands, this leads to knives being able to do a substantial amount of damage to overcome armor.
But it still has a problem; it leaves no distinction for getting through armor. I've seen testing on smaller knives where a dollar store T-shirt put over a chunk of cheap meat was enough to provide substantial protection. Un-clothed meat took drastically deeper slashes on a cut, but stabbing with the point and then cutting allowed for extremely deep wounds. The alternative is to give piercing weapons a small armor divisor, to represent their focusing of the energy. (.5) to (.75) would go a long way towards making points interact with DR in a more realistic manner.