Each humidifier design has particular advantages depending on your specific comfort and health needs. Select one with a tank housing and wick materials that are antibacterial. These designs are also easy to clean out. A humidistat is a plus, but evaporative models tend to self-regulate the moisture output even without a humidistat. I use this type in my own home.
Many models are available with replaceable paper wicks or permanent wicks.
The newest design concept uses continuously cascading water over the wick instead of the wick being submerged in water. Hot steam mist humidifiers are effective. Although the multiwall housing stays cool, the steam outlet may hurt a child's hand. A warm mist design combines a hot steam mist with a cooler air flow for safety. It uses the most electricity of all the designs to boil the water and for the fan.