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Personally not keen on the battery powered vacuum cleaners as my concern in the longevity of the batteries.
Like @Currid mentions, I know a Henry or another plugged VC is likely that they would still be working in 5 to 10 years.
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I got a Dyson V6 about 4 or 5 years ago and the battery still seems fine. It probably won't last 10 years (although there are still replacement batteries available so a decent chance if I replace it) but just being able to grab it and vacuum rather than assembling and plugging in means that it gets way more use than the Miele I have.
I'd say that regardless of which manufacturer a good battery powered one is much more useful than a mains one. So much more useful