Hi There,
I have both types of humidifier for my little boy and i think they are excellent . Warm-mist and cool-mist humidifiers are equally effective in humidifying the air   In general, a cool mist vaporizer or humidifier is preferred over a warm mist one because of the risk of your child getting accidentally burned. A cool mist humidifier can be especially helpful for kids that have coughs.

Hope this helps

Jackie