I guess because we lived close to Illinois Eureka was more popular where I grew up. There were not many folks who owned Hoover and most were Eureka canisters.
Personally, I have always felt that Eureka cleaned better. The Vibra-groomer 1 has stood the test of time. I would agree with Hans that the early models did drive much better due to the weight of the metal base.
Kirby and Electrolux were very popular as was Air-Way. Not many folks owned a Filter Queen or a Rainbow.
Growing up with a Kirby and Working with Royals at the school, those are the machines I am partial too.