Of course the higher you are, the better it is. But you don't want to be TOO high, as that would reduce the number of targets you can grab (the ones just above your humanitarians limit). Also being higher NW means a higher upkeep, so too high is also not a good thing.

The best indicator of performance is land size. The best countries are usually the ones with more land, and they have more land because they started off with a more efficient country (i.e produce more goods per acre of land) at the get go from the first week of a reset. Producing more goods means you can buy more units, get more land, and spiral up.