Rather than a dust bag, the dirt collected by a water filter vacuum cleaner is caught by the water in the appliance's tank. This is an excellent option for allergy sufferers because it can effectively filter out dust particles and larger pollutants. In our daily life, the HEPA filter is the most efficient filter we can find. It has a 99 percent efficiency rating and can remove even the finest particles. In and of itself, this is admirable. If I had to choose between the two, I'd go with the HEPA filter. However, a device that incorporates both technologies would be the greatest option.