OK, thanks again. Personally, I prefer bicubic for downscaling, but it's only because I prefer the rendering of the first image in the "Minimation" section of
this well known visual comparison. I suppose that bilinear might be better or at least as good in the case of real live images. And anyway I'll stick with the ReduceBy2 (bilinear) filters for now, unless someone can prove that it's not the best solution.