Again, personal preferences play a big role in the dust bin choice. I like bagless units I can empty into the trash rather than bags I have to remove and replace, though usually those translate into smaller dust repositories. However, if you have people with allergies under your roof, keeping things as sterile as possible in a removable bag might be a better choice. The other factor to protect those with pet dander or hair allergies is choosing a unit with an air filter. HEPA grade filtration is designed to filter the air moving through your machine, removing minute particulates like dander and allergens. Even in households without allergy concerns, a HEPA system is nice because you won’t be reintroducing what you just cleaned back into your atmosphere in the air expelled from the vacuum. Note that a HEPA filter will need to be replaced. Other designs have washable filters, which you should want if you aren’t considering a HEPA model. Dander and dust can build up in any filter over time, and that minimizes its effectiveness along with the power of the vacuum.