It would likely come down to cost/points for me. AC has better hard product (seats, IFE, Wi-Fi), NZ slightly better soft product, but it would be close. If you are booking on points and you book a Business Flexible ticket you get access to the Signature Suite. Sometimes the points differential can be fairly small which can make it worthwhile. There isn't really a right or wrong answer here, but I'd likely lean AC cost/points being equal.