I remember watching this at one point whilst also checking out review/comparison sites:
our three tester families- put three popular cordless vacuums cleaners to the test
www.bbc.co.uk
I can remember at the time the review sites basically only had Shark come out the top in the 'Best Shark' product. I think the Shark has a better run time, and it seems brilliant at helping bring the carpet pile back up making it look good, but they don't seem to be the best for actual cleaning.
Having said that, I've also had a s*** cordless Dyson. Basically I went back to a corded Dyson and find it brilliant and would also consider Sebo or Vax for my next one given REAL cleaners seem to approve.
Basically the Watchdog thing kind of showed that people are taken in by Shark's gimmicks, and that is probably helped even further by influencers pushing it! Who cares if it actually works the best for similar priced alternatives?!