The best electric smokers are controlled by a thermostat. Instead of the guess work involved with high, medium and low settings, thermostats allow you to choose the cooking temperature you desire and leave the unit during the cooking time. The better models also have automatic timers that will shut the unit off for you after the appropriate cooking time. This has saved many a meal from a distracted host or hostess.
The best electric smokers will also heat up enough to get wood chips or wood chunks smoking enough to impart good flavor. Models that do not have a high enough heat setting fail to do this. The result is little or no smoky flavor in the meats or other foods. Adding more wood will not help, because the temperature is the problem.
The best electric smokers will also be energy efficient. Energy efficient models will be far cheaper to operate than charcoal smokers in the long term. Models with accurate thermostats and timers can be set and left alone for long periods of time. Many are able to set a brisket or other dish on in the morning before work and enjoy it for dinner that evening. This is perfect for when you are expecting company.
Models with larger grill areas may be more desirable than several grill racks with small surfaces. If you want to use the unit for large cuts of meat, like racks of rib, some smaller grills will not suffice. If you are cooking for large crowds and prefer to serve lots of hot dogs and other single portion cuts, more racks with smaller surfaces might be perfect for your applications.