Honestly, I prefer using a vaporizer. It seems to keep the room and the baby warmer. But, I think doctors don't like them because of the potential of children getting burned and they don't seem to last as long because of minerals that are in the water that build-up on the heating elements.
Use a cool mist humidifier during the day, but at night set up the vaporizer on the floor near the baby's crib...NOT right next to it/below it, etc. Before you get baby up in the morning, unplug the vaporizer and put it away, as they can cause severe burns.