Judging by comments I have seen online, some people say Sharks are wonderful, some say Dysons are wonderful, some say Sharks are rubbish, some say Dysons are rubbish. Have you looked at the Which reviews? Funnily enough I've got a load of stuff in front of me at the mo, because I'm toying with the idea of getting a cordless vacuum, and I see that Which does compare the two (though not necessarily the models you are looking at, I guess).