The main difference between the two is obviously one is a sprayer that you pump either manually or by use of an onboard small engine. The sprayer models are typically much less expensive for the unit, but use more chemical. The other uses a small engine to create a fine mist. Misting is the most efficient method to apply herbicides and insecticides. By spraying a fine mist, you can reduce chemical usage and cost. These are typically more expensive for the equipm