Quote: Well in most cases 6 megapixel is enough, especially now that people only watch pictures on their computer screen with HD resolution.
1. Won't a good 16MP sensor and lens will catch more tonal variation (luminance and colors) than a 6 MP sensor of the same size?
2. Post-processing can bring out those variations -- and there is more to bring out in the 16 MP image.
3. So it would seem that downsizing the processed 16MP image will (often?) display more of the tonal variation than a less-downsized 6MP image. I don't know enough optical physics to prove it.
Analogy is not proof, but if you have a high hill and deep valley and you happen to sample the peak and the bottom, more variation shows than anything you do with a shorter hill and more shallow valley.