So is the warm air or cold air unit the better humidifier for the home and are a couple smaller ones up and down stairs a better deal than one "whole house" unit

Depends on
the size of the house
the type of heating system
whether ducted or not
heat pump, furnace, boiler
the climate around the house
the tightness of construction
the age of the house construction

www.heatpro.us energy businessmen's knowledge

Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.