I have a 13 CVO road King with the Daymaker head light. I had a Skunk with the daymakers which I traded on the 15 CVO road glide ultra. I live 20 miles from town, down very curvy roads, the last 3 miles has many sharp curves and its a 160 degree turn into my driveway. All very dark, no street lights and few homes.
Not much difference at all in what I can see in the dark in a curves or turn. The only time I notice the difference is the slow 5 mph or less 160 turn into my drive. I ride a couple times a week in the dark.
13 inch shocks are a huge improvement in ride over the 12 which my 13 SERK has and what my 09 SERG and my 12 SERG had.
My 15 SERGU has the 13, but I think factory air shocks suck. I have 13 Ohlin's on my SERGU now, rides so much better than my others did. Seriously looking at putting 13 inch ohlins on my SERK.