Thanks for the comparison Justin, it is quite interesting to see the various examples side by side.
I'm not sure if it wishful thinking, but I believe that I can just make out some very subtle differences. It appears that the noise reduces from L to R as you stack more frames (improved S/N) and there is slightly more "crisp" detail on the 10% image.
I suspect that if you just showed me these one at a time, in random order, I would probably not be able to pick them.
I guess on a night of good seeing the detail would be sharper and more clear on the best frames in the stack and this should then be reflected in the final IQ.
Good stuff!
Cheers
Dennis