Msd ignitions have a inverter power supply which steps 12v up to a regulated 300volts it's then timed with the coil to pulse on for a period of a couple of nano or micro seconds seconds, cant remember which off the top of my head as opposed to fractions of a second with a regular coil points.
The combined time the coils on for verses the voltage applied equals the total power consumed by the coil
So Msd's ignitions matched with coil puts out heaps higher voltage and current but for a shorter duration