I understand what they says in the two of video were about same, but find difference in their animations. One obvious point I found was the map. When they use a world map to show where the three mile islands and Chernobyl are, the center of the map is different. In the Genpatsukun, the center was Japan while in the Nuclear boy, was near atlantic ocean.
I thought it would be effective to explain the accident in Fukushima nuclear plant for children. The reason is not only because it was easy to understand, but also it was attention grabbing way of explanation. For example using words that are more familiar to children, such as "poop" or "medicine". The use of those words would make it easier for them to catch the idea of what's going on in the nuclear plant.