Five years in, here are my takeouts that are things outside my personal situation that would put me off Auckland vs London. From a UK expat POV, not slagging off NZ for the sake of it!
The cost of living is higher. I can't survive without a car. Home and contents insurance is $2500 compared to a similar size/value house in London that was 400GBP. Food is very expensive. Rents, mortgages comparable but everything else is difficult.
Not as many job opportunities and lower wages. There will always be exceptions but this is the norm. There is no nil rate tax band which hits hard now I'm on a low salary.
The education system is not as academic which is a problem if you are planning on returning to the UK with teens who simply could not slot back into GCSEs or A levels. There are options to study the Cambridge curriculum but these are private schools who are massively oversubscribed.
I cannot sign my daughter up with a local GP and at 14 I have to pay for her GP care. I cannot afford insurance and cannot get public health care for a knee problem.
Annual leave sucks. A lot of companies have a mandatory shut down at Christmas. My company closes for 3 weeks and I must take 3 of my 4 weeks then. It makes travel home difficult if you want to go in the UK summer.
Another UK expat problem is that no one with school age kids will visit you (unless they get longer private school holidays). I hadn't really thought about this because of course everyone said they would visit when we left, but when would they come? No point coming in NZ winter when they get their long school holidays and two weeks at Christmas is not enough.
Flight prices have not really improved since covid with decent routes costing around $4000 per flight during school holidays.
There is more rain than London. This was a facetious point until 2023 when Auckland was flooded and 50% of my house was destroyed causing $100k of damage that took over a year to repair.
Winter is grim without Christmas and going out culture.
I obviously have more emotive reasons, but feel these are fair and representative (of London vs Auckland).