1. Warm mist humidifiers boil water and generate steam which humidifies the air. But, they are a burn hazard and consume a lot of energy.
2. Cool mist (non ultrasonic) work like miniature swamp coolers. They are essentially fans which draw air through a wet paper wick. The Honeywell mentioned in the article is of this type. The fan is however very underpowered and it doesn’t work well in anything bigger than a small bedroom. Vornado makes a version with a much more powerful fan which works very well in large rooms, but their tanks are finicky and prone to breaking and leaking. The wick absorbs minerals in the water and will eventually have to be replaced.
3. Ultrasonic humidifiers: A vibrating diaphragm will aerosolize water. Unless you use distilled water, minerals in the water will turn into dust and reduce air quality.
I happen to like the non ultrasonic cool mist ones because they use less energy than the warm mist ones and replacing crusty wicks is cheaper than using distilled water in ultrasonic ones. The problem is everything currently on the market has issues. Any company making incremental improvements to existing cool mist humidifiers will probably get a lot of eager buyers.