Vac your floors with a new bagged cleaner using a new bag, then
when
you think they are clean, fit a new bag and see that your cleaner
thinks your floors are really clean. Now take a new Dyson and see how
much crap you pick up from your supposedly clean floors. NO ONE who
sees this would ever use a bagged cleaner again unless they were
terminally stupid/filthy.

Oldest trick in the book, often used by Kirby or VK sales people.

Every time you vac a carpet you will get more dirt out of it. Try the
'test' the other way around and it will proove the bagged machine is
better.

Dave