The Dyson vacuum cleaner is better than other vacuum cleaners because it uses little cyclones (like a tornado) to create the lower air pressure while also ensuring that the dirt is thrown to the side of the container and out of the air flow. Other vacuum cleaners use a fan to extract the air from the container, but the dirt gathers towards the fan and blocks the air path, so the suction is reduced.
So cyclones are better.
I had a look at some vacuum cleaners today and saw that most of them claimed to have some kind of “Cyclone”. I wasn’t convinced, so I dismantled a few of them, and was annoyed at my discovery: almost all had fake cyclones! They produced suction using a big fan, just like non-cyclone cleaners; but they had additional bits of curved piping to make the dirt spin around in little powerless cyclones. The dirt still gathers in the path of the air flow, so they still lose suction. But the casual observer would see the spinning dirt, just like they see in a Dyson. Most people would probably not notice that it was spinning much slower than the Dyson dirt. And at half the price of a real cyclone cleaner, most people would probably fall for the trick.
I didn’t buy a vacuum cleaner: I bought a floor brush.