I moved from 2degrees to Spark because of data coverage. 2 years ago in central Wellington, a couple of buildings away from the beehive, 2 degrees data coverage was awful. 2 degrees phone coverage in the Wellington area is poor in some areas, like the Ohariu Valley, and because it's in an area they think they covered but didn't really it wouldn't roam to other providers. 2degrees may have better coverage now.

I'm happy with Spark. Service is good, coverage is good, data speed is good - especially on 4G where it's faster than WiFi on fiber.