Forgive my ignorance, A/M ignition

[NoDOHC]

I don't know about AEM A/M modules, but the MSD is typically a capacitive discharge ignition system. It drives the ignition coil at a higher voltage, but with comparable energy. This results in a high spark driving voltage but very short duration spark. At low speeds, CDI (Capacitive Discharge Ignition) systems will typically deliver multiple sparks in case a single, short-duration spark fails to ignite the charge.

CDI used to be the best way to get high energy ignition. Modern Inductive ignition systems are very comparable and are probably superior in boosted applications. The CDI system can usually be easily retrofitted into the system or even piggy-backed on the factory ignition system. High-energy inductive ignition coils (like LS2 Coils, etc.) will require a revamping of the entire ignition system and probably an aftermarket ECU.