The filter is part of the airflow path
As resistance rises, some systems move less air. That can affect comfort, noise and equipment operation, especially when the filter cabinet is small.
Surface area changes the equation
A deeper media filter may provide more area than a thin filter at a similar efficiency level. Cabinet fit and sealing are as important as the number on the package.
Match the solution to the concern
Dust, allergy concerns, smoke particles and microbial growth are not identical problems. Filtration may be combined with humidity, source control or targeted air treatment.