benefit of shooting at lower mp with the 50D

this is somewhat in response to the dpreview on the 50D and this forums response to the 40D and 50D noise comparisons. One argument is that the 50d has too many mp making it noisy and not really worth the upgrade noise wise. Now what if you shot at 8mp instead? Would that help out the noise? If people really arent concerned about mp than this should be a great solution if it works.

The only difference you will come away with, is a smaller image. Reducing the image size wont effect the amount of noise.

Noise tends to be a factor of how small and close together the pixels are. The pixels coerce each other. As the ISO goes up, the sensor heats up and the coercion increases to the point of creating noise that is very visible.

The only way to achieve less noise is to have larger pixels and more space. As the sensor is a fixed size, the high pixel count works against you.

What does the pixel binning do then?
only activate half the pixels (roughly) making the image roughly 8mp? Or does it let pixels merge (since their gapless microlenses) to create an 8mp image with larger pixels than the 15mp image?