I am a Mopar guy, really never got into GM, but I am an honest engineer, I look at the facts.
You have to remember the HEI is a mid 70's design, the Mopar module a few years earlier. The HEI design is more robust. Often engineers when designing a competitive product to catch up, they improve on the design. They then went overboard, with coil in cap and large plug gap.
The Mopar VR distributor has its share of problems. The reluctor is a powdered iron part, it lacks precision. It has small radius, and small teeth. The distributor uses bushings. The rotor hat fits loosely on the reduced 5/16" shaft. The advance plate, swings an arc, and has rough movement. I can go on and on .... The greatest problem from an electrical standpoint is the variation in timing from cylinder to cylinder. This is mainly due to run out, and the reluctor picking up magnitization. I know this because I have evaluated a few distributors, captured timing trigger signals and evaluated the timings. Things can be improved, but it is a bit like polishing a turd.
Most do not know the difference. How many use a degree wheel and timing light on each cylinder to measure individual timings? How many notice a periodic waver in engine sound? That can also happen with mismatched compression, intake and exhaust flows. Most engines ping first on one cylinder, that has much to due about timing variations.
A GM distributor has a different VR sensor assembly with 8 teeth, 8 pickup poles, one coil. There is a larger change in reluctance, because all teeth come together. It also is an improvment, eliminating run out related errors.
In the motion control industry, VR sensing is for speed measurement, not typically used for position measurement. I like optical or Hall vane sensors. They are zero speed, so it is easy to do static timing measurements. If you want the best, consider crank triggered, with cam sync signal and coil on plug, as part of an engine management system.
