which do you prefer - north island or south island?

For those who have been there, or who live there, which do you prefer? I've heard that the north island has less spectacular scenary. However, it has activities such as zorbing that the south island doesn't.

I guess it also depends on what you're looking to do, viewing great mountains or participating more in adventure activities.

I've heard that most NZealanders live in the North, especially Auckland. But the south island is bigger?