I think both maps are useful, it just depends on what information you are concerned about. The first map only shows the earth crust, so it's useful if you're o

I think both maps are useful, it just depends on what information you are concerned about. The first map only shows the earth crust, so it's useful if you're only concerned with that. The second map, with the step at 0, raises the perception of a "hidden" feature, which is the ocean level.