I always thought it was a function of light and lenses, rather than sensor technology - i.e. the smaller the hole the light passes through, the greater the effect. So diffraction effect at f22 is the same on 35mm or 10x8"
Only real difference being that the effect that the diffraction affects the final image is also a function of how much enlargement is needed to get to the final image size - so for aps digital it's more problematic than full frame or proper 35mm, and its less of a problem as you get up the scale of film sizes - so at 10x8" you could shoot all day at f64 and print at 20x16" and not see any effects whatsoever.