Well, I didn't get everything done yet, but here are two links to low light video same scene on C5/C6.
Please note the time / date for the C5 was still set to Japan - the videos are shot only a minute or two appart.
Low light - indoors with only some 30w halogen spots on the artwork. I used this area since it is challenging going from dark foreground to with bright background objects and reflections off of the framed art.
Quite a difference - please note the reduction in auto-focus / zoom noise as well.
Both cameras were set to multipoint auto-focus / highest video quality ([email protected]
I will try to get to some other comparisons soon.