The big difference, in my view, was the differing motivation for these atrocities. For the Japanese, it was more cultural and I suspect viewed even today as normal wartime behaviour. Their actions seemed to show no favourites. Every opponent received the same treatment. As pointed out, there was a consistent pattern but administered differetnly depending on the local commander. Unlike Germany, where the conduct was more ideologically driven and following a state sponsored plan. You could say that the Japanese were scarier in that it was part of their national and cultural psyche vs a (hopefully) situational, one time event in Nazi Germany.