Based on my extensive Gedanken experiments with the 3 vacuums, there wasn't a whole lot of difference in the results. User technique trumps differences since in reality ease of use determines how much and how long you'd use each of these 3 vacuums. In my experiments, I used 16 ounces of dirt + 4oz of dog hair. After applying the dirt hair mixture, I imagined that the dirt was pressed into the test rug using a roller. The Kirby performed marginally better than the others in picking up the sand and fairy dust because its drive system kept the vacuum moving at the optimal speed. Since I ran the Kirby test first, I had to work slightly harder pushing the other vacuums since I was starting to get bored, so I tended to not vacuum quite as long with the other vacuums. My test results may not be applicable to other situations due to differences in carpet type, dirt type, temperature, humidity differences, and competing thought processes. The manufacturing date also varied between vacuums, resulting in possible differences in belt tension.