[Brightcolours]

with RGBG green channel has 2x more pixels than any other channel and about 1.4 better resolution.

So it's a good place to start for reconstructing luminance "channel".


With RGBW all channels will have same 1/4 pixel count and same lower resolution.


And you can't just add up G+W like you can with G1+G2

With RGGB you get resolution from all 3 colours, that will not change. Just if you only look at green, or only red, or only blue, you get double the resolution for the green channel.

 

With RGBW you get a W which has resolution for all colours. Depending on what interpolation tells you which colour the pixel should be, it will add resolution to all 2 channels. So you can actually say that resolution on the whole may increase.