Have you ensured every setting is the same for each scene select? It is a pain, and I had to go all OCD to get it done right.
Maybe I don't have a setting turned on that changes when a scene select is changed. For instance, maybe the noise reduction setting acts differently with different scene selects, but I wouldn't notice it since I have NR turned off.
Also, mine is a NX720 - which could very well have different results.
If you have found differences, I would love to add your results to the chart.