Hi there, the New Zealand market is a fairly small one - there are only 4 million people in New Zealand all up, so there isn't a lot of cash to go around in the local market.
Overseas commercials etc that shoot here tend to shoot with production companies that use established guys (with obvious reasons) but if you have a very compelling CV you might do ok as an owner operator.
New Zealand is an awesome place to live - you can have an awesome life without very much cash compared to a lot of other places, simply because of the natural environment, but it's worth getting used to the idea if you are looking at coming over that there really isn't all that much work.
In Wellington you do have Weta and Park Road Post and awesome world level facilities that can attract international features - but there isn't the on going smaller work necessarily that you would see in other markets.
Auckland has a bit more ad work coming out of it, and there are a couple of companies that shoot overseas productions on a fairly regular basis (like The Sweet Shop) but at the moment due to the international recession everything is getting tougher, and it certainly hasn't been easy in the last 10 years or so from what I understand.
International Features do shoot both in Wellington and Auckland, but not on a really consistent basis, there are a couple of international Sci Fi Drama series shooting in Auckland at the moment (Spartacus and Legend of the Seeker) although I am not sure if they are shooting Red yet. I know one local show shooting Red in Auckland right now, but the budgets for an entire series here are less than a single episode of a primetime US show (the current red shot drama is the most expensive shooting to date, and their funding allocation from NZONAIR, which generally equates to most if not the entire budget, is $600,000NZ per ep - that's about $350K US an ep, and that's probably far and away the most expensive locally funded production that's been shot here in ages, so whether it gets a second series or not is a fairly random question.
In short, there is work potentially in both centres, but don't expect it to come easy and don't expect to earn major US centre dollars.
I'd say Auckland more than Wellington unless you get in with a Wingnut/Peter Jackson production (who understandably has his own sort of production centre around him fully stocked with some of the world's best talent) - with The Hobbit coming up though (and the definite possibility that it may shoot some flavour of Red One camera) there may be a bit of a production boom down there.
I'd haphazardly equate to the New Zealand production environment to something like Canada, only way smaller in terms of ongoing work, with the odd huge production due to our natural assets (In the film world at the moment being Landscape and Peter Jackson primarily).
My advice would be take a holiday here first if you can find a way to, a month or two, and if you absolutely fall in love with the country (many do) then you'll probably work out a way to live here irrespective of the work environment.
I wouldn't move here with work as a motivating factor - while we bat above our weight internationally those projects are relatively few and far between, and we just don't have enough every day advertising etc dollars being spent to support a thriving local production market - especially in this economy.