I used an S4S on a recent redfish trip. It was a 9' 8wt 4 pc. It was a delight to cast. Very light and fast. To be honest, I think the GLX CC, Xi3, S4S, and Orvis Helios which are probably considered the 4 top end rods right now, are so close in terms of weight and action that you would need to cast them side by side to tell the difference. It appears that each has developed new resins that are lighter and stronger allowing for thinner walls on the blanks and thus much lighter rods. All have a very fast action as well.
Accuracy of each would be the attribute I would be most interested in. Would be fun to test them all side by side if you had the opportunity using the same lines and reels.