That's a good question.
Every list member would consider themselves to have a riding or an electorate, though they're not directly elected by it; they're elected by the nation at large. All of them will stay in office in some part of the country, which would usually be where they live, and so most cities and towns will have two members' offices, the first being that of the electorate or riding, of the person who holds that seat, and the second being that of the list MP who is based in that area.
The only requirement is that the second member make it clear to everybody on their signage and business cards, etc. that they are a list MP based in a certain area and they are not the MP for that area. Both kinds of members would spend the same amount of time in Wellington, and, I would think, the same amount of time in their offices out in the rest of the country.
There's really no difference in what they can do, or how they would behave and go about business in Wellington. I think list members in particular have acted to minimize their difference out in the population at large as well.