I think these maps are fun to look at, thanks for the work.
As an aside, I'm not sure either map is more "fair" in terms of weighting to population size. Of course larger populations will have higher chances of fields medalists, but you get diminishing returns once you hit a certain size due to how limited the resource of fields medalists is.
Putting it another way, there have been only 60 fields medalists to this date (I think). If China won all of them, their density would be 0.0427960057, while if new Zealand won just one, their density would be 0.196695515.