Wellington City Council is currently conducting a postal referendum on the electoral system, asking voters to choose between retaining STV or switching back to the old FPP block-vote system. If you're on the electoral roll in Wellington, you should have received voting papers in the mail over the weekend. They are due back by 12 noon on Saturday 27 September, but its probably best to post them early, just to make sure.
As for which to vote for, I'd say STV. It's democratic, it's proportional, it gives voters more choice and control. Whereas the block vote - FPP in multi-member wards - is about as undemocratic as you can get, and allows a plurality to leverage itself into absolute victory (something I've seen happen far too often in Palmerston North). I know most people don't care about local government - but if you do, or might, then please vote for the democratic system rather than the undemocratic one.
Further information on the two electoral systems is available here.