A tweet from J.M. offers this sample of video taken using the internal recorder with the same settings, old vs. new firmware:https://www.dropbox.com/s/vuwbn2582pv67i3/5d3121.png
So maybe I actually was correct in my initial take (a post I since deleted) where I said it looked like the video was sharper. I first I was sure that it was crisper, but then I decided I had tricked myself.
Internal vs external seems similar but new vs old firmware seems different.
Maybe it does grab more details and not mush details in shadows as much now.
(I think I have seen a few very weird artifacts with the new firmware though perhaps popping up in video. A couple nasty weird things, but not sure yet.)
(It doesn't look as crisp but artifact free as the 'raw' DNG stuff ML discovered though.)