Hmm..
The best?
I'd say the best ones were the Dirt Devil platinum force upright, and the hoover windtunnel twin chamber machines (with the diverter). Both of them had fairly short airpaths and larger filters which I feel gave them an edge over most of the available machines.
The worst?
The Eureka Maxima. It had a smaller filter which clogged instantly and probably 5-6 feet of hose for the air to flow through. It is probably the worst vacuum i have ever used.