Surely it's easier to just max the res (and possibly hit 2160p) of an XO game with XO settings on 1X than to implement checkerboarding.
If checkerboarding is implemented in the engine already, then the work required is obviously less to use it than having to retrofit it.
I don't think checkerboarding has come about because of 4Pro being weak, we had already started seeing engines start to use checkerboarding (or some other smart rending) on PS4 and XO.
The fact that it has ID Buffer support though has definitely helped it.
1X supports checkerboarding, what that support actually looks like no one knows, may not be any more than XO or PS4.
My question is does the ID Buffer only help with performance, and ease of development, or does it actually help with IQ (may help track temporal information better?), and if so how much compared to without?
Could a 4Pro CB image look better than a 1X CB image (if there is no additional hardware in 1X)?