Trying to sort things out at the perceptual level, it appears to me that EWA RobidouxSharp through linear RGB is generally both sharper and (this is the important bit) has less noticeable haloing than LWGBautolevelGamma3s100. And yet it introduces less moire.
EWA Mitchell through linear RGB, for example, looks really good in the sharpness/halo ratio department. Nice balanced scheme.
Am I missing something? (Away from my large calibrated monitor, but I don't think it matters.)
P.S. OK. Maybe LWGBautolevelGamma3s100 is a nudge sharper. It's less sharp than EWA CatRom through linear light, though, and CatRom does not seem to add an amount of haloing that matches the additional sharpness.
What I don't see is obvious advantages of the new downsampling methods over simply pushing the Keys alpha up from 0 until the sharpness is sufficient.
Again: Am I missing something? (I hope I am.)
(I reserve my opinion w.r.t. upsampling. Different game.)