I have owned both a Kirby and the Rainbow vacuum, and you did well to buy the Rainbow, in my opinion. They are not only a much better vacuum, they also can be used as an air purifier.
If you detach the hoses and set it in your bedroom for about 1-2 hours before you go to bed, the air in your bedroom will be all fresh and purified when you go to bed, and it will also help to keep you from catching a cold bug or flu.
You can add something like eucalyptus oil, or Vicks to the water in the Rainbow, and that will also help the air in your house to be more germ-free.
The demos of a Kirby are designed to make it loook really good because they use special little cloth filters, clean a little space, and then take out the filter to show you how much dirt and dust the vacuum has picked up, and then they use a new filter.
If you are actually using the Kirby filter bag, it will be pretty much clogged up before the bag is half full of dirt, and then it has lost most of the suction power.
If you notice, the Kirby people almost always have some little gadget that the husband will use that comes along with the vacuum cleaner. They learned that the man will not spend over $1,000 on a vacuum for his wife; but if it has something that he can use in his shop (or somewhere), then he is much more apt to buy his wife the Kirby.
I sold a vacuum cleaner called the Extractionaire for a while, and part of our schooling was to learn about how other vacuum cleaners worked. The one I sold was similar to the Rainbow, but it was built like a miniature steam cleaner (like you can rent at the grocery store for your carpets), and made by Thermax.
It also had a special attachment that made it into a water filtration system vacuum like the Rainbow is, so it was great as both a carpet cleaner and as a vacuum cleaner.
Rainbow was first called the Rexair, and my very first vacuum cleaner (back in the early 1960’s) was a used one of the Rexairs, and it was an awesome vacuum, and unique for its time.