First off, you should know that I lived on the South Island for the 4 and a half months I was in New Zealand. Most of my travel was around the South Island, so I may be a bit biased. However, I did see a decent amount of the North Island as well (most everything except the East Cape and the westernmost part). My extensive amount of travel within the country makes me feel somewhat qualified to judge this (but share your views in the comments!).
There are two criteria I thought of that have no obvious winner. These are food and cost. Neither island has clearly better food (it’s not very different) and neither one is clearly more or less expensive. So far then, we have a tie. Let’s see how they fare in some other categories.
The North Island is mostly rolling green hills, with some stunning volcanic landscapes. The South Island is extremely mountainous, and yields up breathtaking views at just about every bend in the road. They are both really beautiful, but for me the South Island is just more magnificent.
Winner: South Island
Most of the largest cities in New Zealand are on the North Island. This shouldn’t be surprising; about 76% of the people live on the North Island. The four cities I’m considering here are Auckland, Wellington, Christchurch, and Dunedin. The first three are the largest three in the country. The fourth is where I lived while I studied there. Auckland is nice but wasn’t my favorite. Wellington is absolutely lovely – it strikes me as quite similar to San Francisco, my favorite city. Christchurch is also incredibly charming. Dunedin is lovable but a little dirty in the university areas. If you’re a city person, you’re going to most likely enjoy Auckland, Wellington, and Christchurch very much.
Winner: North Island
New Zealand has 14 national parks, only 4 of which are on the North Island. Nine are on the South Island, and the last one is on the third biggest island, Stewart Island. I’ve been to one national park on the North Island (Tongariro) and four on the South Island (Abel Tasman, Paparoa, Westland Tai Poutini, and Fiordland). While Tongariro was absolutely gorgeous (and home to probably the best day hike in the country), the beauty of the South Island parks, as well as the fact that there are so many more of them, give them a strong advantage.
Winner: South Island
New Zealand is known for its adventure sports, and for good reason. Almost everywhere you go has a ton of crazy cool things to do that will get your adrenaline pumping. Waitomo on the North Island is home to caving adventures. In Rotorua, you can raft the world’s highest commercially rafted waterfall (the 7 meter Tutea Falls on the Kaituna River). Taupo is well-known for skydiving. On the South Island, you have a veritable feast of options for adventure activities. Queenstown is known as the adventure capital of New Zealand. I went canyoning, bungee jumping, and jet boating there. Nearly anywhere on the South Island will have something to get your heart pumping, but Queenstown, Wanaka, Christchurch, and Nelson/Motueka are the hot spots. Both islands have an amazing array of things to do in this vein, but I think the South Island has just a bit more variety. If we were going by how much I enjoyed each activity, caving would be at the top, closely followed by canyoning. However, since I’m basing this on variety and availability, the South Island gets it. [Note: I went horseback riding a couple of times on the South Island, too. But since I grew up riding, I don't count it as an adventure sport.]
Winner: I hardly want to decide, but the South Island has a tiny edge.
The native people of New Zealand are the Māori. A fun thing to do is going to see a cultural performance, where you might see the haka and poi, and have a hangi feast. The main place to do this for tourists is in Rotorua, on the North Island. You can also do this in Christchurch. About 90% of Māori people in the country live on the North Island, so there is a very clear winner here. You can visit the Waitangi Treaty Grounds or do a marae stay (I did mine as part of a Stray tour).
Winner: North Island, no contest.
North Island: 2 points; South Island: 3 points.
As you can see, the islands are very close. I loved living on the South Island. The country is not huge, and transportation is easy and affordable (though distances are a bit smaller on the North Island). You can see a lot of the major highlights on either island in a month if you are traveling quickly. If you like being in cities and seeing cultural performances, the North Island is for you. If you like raw natural beauty, hiking, and adventure sports, head to the South Island. Honestly you can’t go wrong with either. New Zealand is amazing!
Have you been to New Zealand? Which island is your favorite?