The white CornishX will normally grow faster than your coloreds, and will dress out roughly 2-4 weeks earlier depending on your feed schedule and dress weight desire. I can usually process my CornishX around 8 weeks and average 5 pounds dressed where the coloreds will take 2-4 weeks longer for the same dress weight.
However, having said that, the coloreds do seem to be more hardy and so much more active and chicken-like than the wide-track CornishX. They are also nicer to look at, according to some -- but I personally prefer the whites for plucking ease.
The white CornishX are more sedate than the coloreds in my experience. The coloreds are not aggressive at all, and your three year old would still be able to handle them as babies and such, but the coloreds do act more "chickeney" and will take better to range and foraging than CornishX seem to.
As for taste, I have noticed a slight difference in flavor, but it was just that - slight. Not enough to favor one highly over the other, personally. Others may be more sensitive to taste differences, but for me, it was nothing to write home about.
