Digital ballasts provide far greater energy savings and light output than you would get from a magnetic ballast. While the older magnetic ballasts took a long time to start the grow bulb, digital ballasts ensure a quick start up for your grow lights, and they run cooler than the magnetic units. Unlike magnetic ballasts, digital ballasts will quickly detect if there is a problem with a grow bulb or a faulty wire in the grow lighting system and turn the unit off, making for a safer operating system.
To increase the life of the grow lamp, a digital ballast uses a soft start model to ignite the grow bulb, rather than flowing a large amount of power to the grow lamp to start it, and then reducing the current to the correct running level. When magnetic ballasts get older, they often become noisy, which is not true of silent-running digital ballasts. When using magnetic ballasts, over time your grow light will give off less light, but with a digital ballast your grow light produces more lumens because the electrical current is sent in a highly controlled digital manner, leveling the flow, and the more consistent energy supply helps the grow bulb run more efficiently, with a side effect of increasing the grow bulb's life.