If you have a large house, you need a vacuum cleaner that can handle the large rooms and long hallways. We would recommend a large upright with a wide cleaning path to handle these large spaces. If you've got lots of stairs, however, a canister might be worth a look.
Big spaces need a cleaner that offers a wide cleaning path, because the wider the cleaning path, the fewer passes are needed to cover the area, which means quicker cleaning. Upright cleaners are also easier to use in big spaces, because you don't have to drag the canister behind you.
Big rooms also often mean high ceilings, which means you need a cleaner that offers a long reach to get up to the light fittings and fans that collect dust. Most cleaners offer hose extensions that increase the range, but the length of these often varies. The tallest reach that we have seen so far is from the Dyson DC28, which can reach up to 5 feet and 9 inches above your outstretched hand.
If you've got three flights of stairs, consider the weight of any vacuum you'll be buying, as you'll be carrying it up and down those stairs and using it to clean them. You may want to get a separate vacuum for a basement, third floor or just stairs. A good compromise might be a vacuum set like the Hoover Platinum UH30010COM. It's an upright vacuum that comes with a separate portable canister vac, which may be good for cleaning stairs and small spills where lugging an upright may not be ideal.