We all know that when bagged vacuums fill up with dust -- or crayon tips and pennies, if you have kids in the house -- there's a steady decline in suction power. Soon, there's no more effect on the carpet than if you'd just pushed four wheels back and forth across it. When you notice that you're only adding lines to the dirt and debris on your carpet, this is your signal to change the bag.
Bagless vacuums suffer much less decline in suction power as the dust collection cup becomes full. Even better, there's less chance of a bagless vacuum being full in the first place because its transparent plastic cover allows you to see exactly how much debris has collected inside the vacuum.
A bagged vacuum needs to have its bag changed frequently, depending on how often you vacuum and how worn your carpet is. Once that bag is changed, you have to retrieve another bag. This is where many vacuuming adventures are cut short. A visit to the closet -- followed by an extensive high-and-low search around the house -- too often reveals that vacuum bags weren't on your most recent household grocery list. Worse yet, you may waste a trip to the store if your particular type of vacuum bag isn't in stock. Once you throw away the old vacuum bag, suction is back to full power; however, without a new bag to insert into the vacuum cleaner, you can't do much cleaning.
Bagless vacuums, on the other hand, are always ready to work. Once you empty the dust cup, you just have to reattach it, and the vacuum's good to go -- no special-ordering vacuum bags or trying to remember where you stored them in the first place. Also, vacuum bags end up in landfills, while bagless vacuums won't contribute to this waste product.
While bagless vacuums have many advantages over bagged ones, there are some major disadvantages, as well -- especially if you have asthma or allergies. What are those disadvantages? See the next section to find out.