When comparing the CS4 to the Kumho, I'd go with the CS4 overall other than price is a little more. From just looking around, it looks like quite a few places online are sold out of them at the moment which also tells me users would say the same thing. Just my input*
Expert with Tires & Wheels - Member of Tire Team - Hit me up if you have questions about your tires!
Ive had mine for only a few weeks, but driven many hundred miles so far. I think the coopers CS4 is very smooth, and one of the quietest tires I have owned. There were parts on the highway, where both my wife and I commented about how there seemed to be next to no road noise at all. It was almost as if we were simply floating on a cloud, that smooth.
Of course the wind noise near the roof, partially spoiled that dream.