Don't confuse print resolution with camera resolution, don't confuse print quality with mega pixels and dont assume more mega pixels means a better quality image.
The 5d2s ability to capture better tonal ranges and more accurately produce colour changes than a 30d has nothing to do with it having more mega pixels.
I don't confuse resolution with the tonal quality I'm referring to. But to an extent the extra MP of the 5D2 DOES have a bearing, along with other atributes, on the tonal range. Accuracy or otherwise I cannot comment about, a "smoothness" of tonal changes is the only way I can explain it.