Have you tried a Shoei Raid II on by any chance? If it fits you well, it's as good as you'll get for around £200. It was on another level from the other helmets around the same price when I was in the market for one.
Oh, and it's a DD too.
Shoei Raids have been discontinued there is a new model out in October therefore there are some good deals to be had
Not sure as I have no personal experience as yet but at night, I wonder if a degree of light reflects off the pinlock back onto the visor, from visor to pinlock and so on Also it may have a starburst effect as the pinlock might not be as refined as the main visor..Also the visor has a stick on it that says "Mist retardant but daytime use only with pinlock" Its a clear visor so why daytime use only?