Slow cookers that receive good reviews must have two key features, according to Techlicious.com. They must be large enough to fit meals for up to eight people, and they must have a programmable timer that shifts to warming mode when the cooking time ends.
The Consumer Reports' slow cooker buying guide states that there was little difference in actual cooking performance of slow cookers. Consumer Reports also suggests that the most important features for slow cookers are a large size and programmability. Consumer Reports indicates that other key features for slow cookers are clear lids, easy cleaning and an easily portable shape.