I have yet to be dazzled by a reflection from my top rib and all my S/S's have smooth concave ribs.
I took a few guns out of the store today and compared the view up the rib between the file-cut (or whatever) and smooth and would make the following observation.
The 'anti glare' finish on the rib makes it more visible to the eye and leads your eye to perhaps be more central to the rib.
The smooth concave surface tends to vanish as it reflects the colours and textures beyond the bead back to ones eye and so one only sees the bead.
However, unless you are aiming at a stationary mark, you shouldn't be looking at the gun rib at all. Your eye should be focused on the target and gun fit should take care of the eye placement.
On balance I think that game or other fast instinctive shooting calls for a smooth rib and anti-glare finishes are best for trap and inanimate target work. IMHO
