Paul Alfred, they make the offer irrespective of your stated “preference” as people often change their minds and get the ****s when they offer the job to someone else “I would have taken that” besides preferences are just that preferences. They also ask you for your preferred base and that is not guaranteed either.
While moving to NZ might be a challenge getting on to the seniority list is, in my opinion, the highest priority.
The list dictates how your career progresses once you are in the airline, so while where you start might be important now, where you finish is probably more important. With so few widebody aeroplanes the bigger aircraft are more likely to be crewed by those further up the seniority list. The later you join the list the lower you are.