We wound up using Behr solid stain in Slate. We chose it because of its scores on a Consumer Reports test and we generally have had good results from Behr products. Our deck "after" painting. We liked the effect of the old Behr semi-transparent Redwood color showing through, so we left it.
After--we did this project about a year and a half ago. The Behr DECK OVER product is holding up well. The only place it chipped off was the edge of a step because people have worn it off. I think this would happen with any paint product.