There are advantages and disadvantages to both designs. In general, bag machines move the air through the vacuum in a more efficient manner and provide considerably more cleaning power. You replace simple filter bags which mean less direct handling of dirt, dust and allergens. Bagless machines require more maintenance to empty, clean and unplug. The expense of replacement filters can exceed the cost of replacing filter bags. If you are unsure, the best idea is to go to Quality Vacuum and try both types to see which type suits you.