Decent article:
http://www.onallcylinders.com/2014/1...tive-ignition/
excerpt: A CD ignition system works a little differently by employing a capacitor to store something like 440 volts of electrical energy. This high voltage energizes the primary side of the coil. As you can imagine, it doesn’t take very long for the primary side of the coil to completely energize. With the primary side energized, the connection is broken and the voltage dissipates across the coil’s secondary windings and a much higher potential voltage is created. The advantage to a CD ignition is this higher secondary potential voltage can jump across the open gap of a spark plug under high pressure–as with high boost supercharged or turbocharged applications. The disadvantage of a CD is that the spark duration is much shorter. That was the marketing genius of MSD’s ignition program when that company started back in the 1970’s. MSD stands for multiple spark discharge. Company founder Jack Priegel said that his ignition could fire three times at speeds below 3,000 rpm to help completely burn the fuel in the cylinder. The reason for this was the CD’s ability to recharge the primary side of the coil very quickly. The disadvantage of the CD ignition is that the spark duration is not nearly as long as an inductive. There are plenty of arguments on both sides of the table as to the advantages and disadvantages of each ignition system.