OK, so a few more of my opinions:
For a mild street vehicle, or a stock engine, a well-tuned and properly curved stock-based distributor and trigger system works just great, as I've noted earlier based on factual testing and real dyno numbers. The Royal Bobcat SD 421 cars were setting NHRA records with stock distributors and points, and we were running points in our 455SD SS/KA cars in the mid-70's. No problem going fast...
Obviously, the makers of the aftermarket systems need a niche for selling their products. Most stock distributor systems are set up pretty lousy, since few people have access to a distributor machine, nor do most people understand what a "good" timing curve should look like or what constitutes a good set of points. So Mallory, MSD, Accel, Proform, and Pertronix can make a distributor with a mild performance advance curve in it and sell it as a "performance" part. When you bolt in the new distributor with the improved timing curve and fancy CD trigger box, you get an instant performance increase. Isn't that amazing.
In an actual racing engine, there are 2 things that put your ignition system at the limits of its capability: Dynamic cylinder pressure and rpm: A high compression racing engine can operate at very close to 100% volumetric efficiency at its torque and power peaks, which means that the cylinder pressure just prior to the ignition point is extremely high. As pressure goes up in the combustion chamber, the resistance across the plug gap goes up, so higher voltage is required to jump the gap. For this reason, racing engines, even with high voltage CD systems, will limit plug gaps to .035 - .045. This assures that the resistance across the gap, under high dynamic cylinder pressure, does not go up so high that the high energy ignition system does not arc across a point with less resistance, such as inside the cap, or off a plug boot. It is possible, in high performance engines, to get the cylinder pressure, and resulting plug gap resistance, so high that a "normal" stock ignition system will not fire the plug. Thus, a high energy aftermarket system would be required. I have never seen this happen in a street-drivable vehicle. Likewise, an engine operating at very high rpm offers very little time for the coil to saturate and produce the required high voltage discharge. Magnetic trigger systems, capacitive discharge, and aftermarket coils offer quicker rise rates, more effective dwell duration, and higher secondary voltage to assure adequate voltage to fire the plugs rapidly under these conditions. Again, street driven performance vehicles seldom see this rpm-induced ignition limitation, and certainly not a GTO with an under-6000 rpm redline.
The MSD- and HyFire-type multi-spark systems typically only multi-spark up through 2500 - 3000 rpm, which is far below an engine's power peak. Thus, they do not create any benefit to peak power. In cars with big cams, running "dirty" at rpm below 3000, the multi-spark systems seem to make the plugs run a little cleaner, and I've subjectively noticed that idle quality can see a slight improvement on cars with lumpy idles. My dyno testing shows no measurable improvement in power from 2500 rpm up with the multi-spark units, so the change in rough-cam idle quality is "cosmetic" only and purely subjective on my part.
Should I start rambling about oil company profits and diesel oil now..?
Lars