Now I actually support STV in many types of elections. In fact I introduced constitutional changes to InternetNZ so that candidates are elected by what is effectively STV, not FPP. National uses a form of STV for its internal elections for candidates and the board. I like and support STV in situations where it works well.
STV works well when the voter has a relatively small number of candidates to choose from, and they know most or all of the candidates. When you know the candidates you can quite easily make an intelligent choice about ranking X No 1, Y No 2 etc.
However STV is an unmitigated disaster for DHBs and a partial disaster for Councils.
Even the most politically active geek has no idea who 80% of the candidates for the DHB are. Trying to rank 30 of them in order based on who wrote the best 200 word bio is just insane, and it is no surprise turnouts are so low.
If one insisted on keeping STV for DHBs, then you would need very very small wards with one vacancy per ward. That way you may end up just raking say four or five people for one local spot – something which might be possible if they are fairly well known locals. Of course whether you want to have geographical segmentation like that for DHBs is another issue.
With regard to Councils, it is not quite as bad. I actually like STV for voting for the Mayor. There is only one position to fill and it is possible to fairly sensibly rank say half a dozen candidates for Mayor. I like being able to express a second and third preference should my first preference fail to be elected.
But then when you come to wards, it becomes near useless again because again not even the political geeks can sensibly rank say 15 people competing for three Council positions. And so we have a 10% fall in turnout over two elections. If you want to keep STV then you need small one person wards.
I could advocate STV for the Mayor, and FPP for Council but that may be too confusing. So if WCC is to have one electoral system only, then FPP is best.