I did some comparative experimentation of ISO 100 to ISO 200 in daylight photography. I think I can see clear difference between the pictures. Much of this may already be documented, but this is what I found first hand experimentation - at ISO 100 I can see - a) more depth, b) more clarity - a much better picture. ISO 200 gave me - a) a flatter picture, therefore lesser depth, b) less clarity.
See for yourself.ISO 100