I've put many miles on the foldable gatorskins, the 4000s, and the 4000Ss, they are all really great performing, durable tires. For durability in the face of evil debris, the gatorskins are probably tops, but the 4000s and 4000Ss are quite good, and I've been amazed at the 4000Ss cut resistance.
For performance, the gatorskins are at the bottom. They feel stiffer and like they have more rolling resistance. They feel (and are) heavier too. The 4000s and 4000S both feel quite nimble, and I don't really feel a weight difference, but the 4000S is really the performance king.
It rolls fast and smooth and feels like it grips much better than the other tires.
The 4000S is the only tire I will buy right now. (Until someone convinces me that the regular black 4000 with chili compound is as good... Then I can save a few bucks, like 3, over the 4000S).
As someone already mentioned, the best prices are at ProBikeKit.com. They are in the U.K. but delivery to me here in S.L.C. is usually 6 days. (which is better than when I order anything from Performance).
BikeTiresDirect.com also has good deals and fast delivery.