The CVO Ultra has 13 inch air shocks. The CVO king has 12 inch hand adjustable gas charged shocks. The kings shocks are a bit firmer, and have less travel. The front on the 14 and newer is also firmer. Between the two it should provide better handling, but a little firmer ride.
I have had a few bikes with the 12" premium hand adjustable gas shocks, and like them. My 13 King has them.
When I got my 15 CVO Road Glide Ultra, I hated the handling. No mater how I adjusted the 13 inch air shocks, it felt like the back end was loose and would wash out in a hard curve. I just never felt comfortable pushing the corners like I could on my CVO King, or the 12 CVO RG I traded for the 15.
Put 13 inch Ohlins nitrogen gas charged on the 15, now it is firmer but it sure handles much better, and can run the corners hard.
So what I am saying is some really like the smoother ride. Others like me prefer the firmer ride for improved handling and performance in the curves.