Which style of knife sharpener you get depends on what you want from the tool. Manual knife sharpeners are traditionally less expensive and have the bonus of not requiring an outlet to function. The downside of manual knife sharpeners is they tend to be more technical to use. An electric knife sharpener is as simple as turning on the machine and sliding the blade through evenly on each side. Do this on all three slots, and your blade is ready for use. If you want a knife sharpener that is easy to use and you don't plan on using it outside of the kitchen, an electric knife sharpener is a good option.