We ended up buying the Vax Blade V4. It cleans very well but is heavier and noisier than the Dyson v10.
On paper the difference is only 300 grams. If I put unit + battery + dustbin on a scale, the difference is more like 500, but it feels like so much more - maybe it's the distribution of the weight. I have to use the Vax with both hands and, after cleaning 3 rooms, my right wrist hurts - it never hurt with the Dyson. I am surprised no review mentioned that. For me it's fine but I'd never recommend the Vax to a senior person.
It is also a bit noisier than the Dyson v10, but beareable.
The dustbin is smaller - cleaning a 5 bedroom house I have to stop and empty it about 3 times.
The suction power is great - no complaints there. On maximum power it is so powerful that it seems to stick to the carpets and it becomes very heavy to manoeuvre around.
There is an on/off button, not a trigger like the Dyson. The Dyson is better because it stops when you release the trigger, so you save more battery.
The VAX has only one head for carpets and hardfloors, no need to switch. The head is a bit narrower (so better access) and has a light, which is not a gimmick but actually useful.
The head doesn't spin automatically - you need to press a button for that.
The battery comes on and off with a simple click, so it's easy to replace. This is a huge benefit compared to the Dyson.
Would I buy it again? I guess so, because it comes with a 3-year warranty (not 2), two easily replaceable batteries, cleans well and costs about half the Dyson v11. The main drawback is the weight: for someone like a senior person with maybe a smaller house (so who doesn't need 2 batteries) an older (so cheaper than the latest model), lighter Dyson might be better