I went around and looked at a great many screens while at INFOCOMM, and I can honestly say that a screen with black bead, light pipe, or black substrate looked pretty damn good. It's really hard to compare them because they're all showing different source material on different projector. I couldn't accurately attribute higher contrast to either the screen or the projector. If you pick up one of these screens you'll get really excellent performance in ambient light, no matter the type of screen. Although, I notice that all of the screens have light splash-back to some degree and that may affect useable brightness and contrast. I couldn't say which screen was better for that or more efficient with light.
The Stewart Blackhawk did have excellent off-axis characteristics in all directions, but competing screen were not too shabby either and I didn't specifically look for good uniformity.
In any case, diffusion or plain lenticular screens did not compare as well. Almost of them have weak black level performance in ambient light and a high degree of hot-spotting.