This depends on what types of particles you want to clean out of the air. An ionic air purifier is good for removing germs, smoke, and pet dander, plus is great for allergy relief, though the odor removal depends on the machine you buy. They also aren`t great at dealing with dust. HEPA filters get rid of dust, smoke, odors, pet dander, and even pet hair, plus can relieve allergies, though they won`t take care of the germs without some sort of germ-killing additive. Though both are fine alone, they do work best when used together.