Just out of curiosity, are you looking at the exact same length of dim?
The reason I ask - in my short time playing with these, dimming seems to have a very 'curious' behavior overall. If you dim fairly fast, your eye seems to blend the ramp into a smooth dim. If you dim very slow, there is plenty of time to ramp through all (or most) of the 255 levels and your eye can't really see the jump. Both of these tend to look fairly smooth. But if you dim somewhere in the middle, the controller has to make fairly big steps to do the dim in a short time, but the steps are fairly large, so your eye can pick them up - the result is a 'choppy' dim.
I haven't played around enough to know the limits of these - but I suspect it may be somewhat of an individual opinion. I know some people who were perfectly fine looking at a 60Hz CRT all day long, but it would give me a headache and practically induce a seizure after a few minutes.