My first ignitor was a Hot Spark, It looks and acts just like the Pertronix unit with the small magnet ring. Worked fine until I had a small melt down, not the hot sparks fault . What I had noticed since I use the megasquirt, and put my scope meter on it to confirm, is during cranking i never got a nice clean square wave signal out of it. Once started , it was fine. This time I opted for the Compu fire conversion, since this has a large disk that passes over the top of the sensor. The disk has small magnets on the outside edge, allowing a higher surface speed over the sensor. Cranking signal has cleaned up by a factor of 2 to 1. My idle is now way more solid than with the little ring magnet sensor type of pickup. So, in conclusion, the signal coming from the Compu-fire is much cleaner, allowing better idle control for my application. 2 weeks in so far. I obviously can not attest to longevity yet.
Either one IMO works well for carbs, or stock FI, but so far, I prefer the compufire for my aftermarket FI.