I wouldn't really consider 1x to win out objectively with the points that you listed as some people weight certain criteria differently depending on their workflow.
I personally design at 1x, but I use Sketch and haven't used Photoshop to design a website in quite a while. I have developed based off of assets delivered by other designers at 2x and it's super annoying to have to redo math.
In Sketch I wouldn't design at 2x. There's no need in that app. If you design in Photoshop at 2x, you can export the assets from the 2x file, then reduce the image size in half before handing off to the developer so no math is involved.
I wouldn't really consider 1x to win out objectively with the points that you listed as some people weight certain criteria differently depending on their workflow.
I personally design at 1x, but I use Sketch and haven't used Photoshop to design a website in quite a while. I have developed based off of assets delivered by other designers at 2x and it's super annoying to have to redo math.