We did the 'tour' of NZ and decided that whilst the South Island is ideal for summer vacations, the North Island rules.
The North Island has more population so more opportunities and facilities, and it has better weather! OK, looking at statistics most of the South Island has better weather than most of the UK but you need to
feel the difference, and that is more likely in the North Island. Nelson and Blenheim are the two areas I would consider in the South Island with their long hours of sunshine, but for employment opportunities Christchurch seems to be the place.
