With 1:1:1 the matrix isn't square, and if you have to double one of the channels for practical purposes then the green one is the obvious pick as it's the most beneficial in increasing the image quality cause it's increasing the spatial resolution where our eyes can actually notice it.

Grab a random photo and blur its blue channel out a bit. You probably won't notice much difference aside of some slight discoloration. Then try the same with the green channel.