> Presumably both the MS-SIM metric and humans would judge RNN better for these portions.
doesn't remotely hold for detailed/high contrast. If I can see a huge difference, and vastly prefer one over the other, the metric is not useful by its definition. Please don't get emotional about figures of merit.
I'm guessing a genuinely useful figure of merit would have put both file sizes a bit closer together, and the NN would have shined, especially since it works so well in low contrast areas.
It appears to be a severely flawed metric.