HA this is where you are extremely wrong. The af100 can't touch the fs100 low light.
i shot the video for this promo, all of the bar/dancing shots are either with a tokina 11-16 at 2.8 or nikon 50mm 1.4 at 2. Shot 21db (6400 ISO) and 24db (8000 ISO) and there is NO NOISE. the fs100 wins the low light battle hands down vs any other camera.
If you really need the best low light performance, the fs100 is the camera. the 5d, 1dmk4 and af100 will also have good low light performance but the fs100 is the clear (pun lol) winner.