For most families, choose a model that produces a maximum of 60 cups of hot water per hour. There are higher-output commercial models available. With small children around, select a model that has a safety-type of lever. Some require a push and a quarter turn before the hot water is dispensed. If you are redoing your entire sink or countertop, you have additional options.
Some models now have both a hot and a cold lever.
One model also has a built-in carbon filter. For steaming hot water, you push a demand button. This is easy to install because you only need to run one cold water line to the new sink. Empty a bottle of spring water into the top. Use the chilled water lever for cold drinks and the hot lever for tea or coffee.