What's a more efficient ignition system, coil and battery or magneto?

A magneto is much more efficient. There are fewer parts in a magneto system which translates to fewer components that can fail. A battery-operated system needs an alternator, starter, battery, voltage regulator and a coil. All of these parts can fail for numerous reasons. This is why the magneto system would be considered more efficient than a battery-operated system.

How is a magneto ignition different than other motorcycle ignitions?

Most modern motorcycles rely on a battery and a charging system to keep the motor running. These electrical systems provide the spark that ignites the fuel as well as providing the power that keeps the lights on. A magneto is completely separated from the rest of the electrical system and will allow the motorcycle to run even if the battery fails. This is the same type of system you will find on most lawn mowers, trimmers, or chain saws. Once the engine is started, it will continue to run on it's own.

If I have a magneto on my motorcycle, do I still need a battery for lights?

You do not need a battery as long as you have a motorcycle stator that is capable of providing enough power to run your lighting system. The stator is like a tiny generator. It produces power when the engine is running. If your stator is big enough, it can produce the power needed to run your lights.

Did any stock motorcycles come equipped with a magneto?

Yes, there are plenty of motorcycles that came stock with a magneto system although most of these motorcycles would be considered vintage bikes. One example is the Harley-Davidson Sportster XLCH, generally considered a 'Competition Hot' model. XLCH Sportsters came stock with a magneto, while the standard XL and XLH models were equipped with a battery and points ignition. Pre-1963 Triumph motorcycles, such as the T120 Bonneville, T110 and others also had a Lucas Magneto ignition as stock. There are still many new dirt bikes that use a magneto system. A good sign that the bike may have a magneto is if the bike has a kick start lever. If you see a kick start lever, there is a good chance the bike has a magneto.