Macbook retina scaled resolution quality

I have a 2nd gen Macbook Pro Retina 15 inch. For pretty much the whole time I have been running it at the scaled 1680 x 1050 resolution (1 up from the "best for retina" resolution).

After randomly playing around with the different resolution, I came to notice that the "best for retina" display is in fact better quality to my eye (so much so that its almost painful to use any of the scaled resolutions now):

I tested this by browsing and reading text at the two different resolutions, making sure to zoom to accommodate for size difference. I even tested it out reading smaller text on the higher scaled resolution with the same outcome. The "best for retina" (1440 x 900) appears less fuzzy and significantly reduces eye strain.

My question is (aside from wondering if anybody else has noticed this): is there a technical reason that could account for what I am seeing?

Solution 1:

Best for retina = every on-screen pixel is represented by four pixels on the display (1440 x 900 displayed on 2880 x 1800 pixels)

More space = every on-screen pixel is represented by 1.8 pixels on the display. (1920 x 1200 displayed on 2880 x 1800 pixels)

In between these two settings every on-screen pixel is represented by an uneven number of pixels on the display. Because there is no such thing as half a pixel, the drawing is not exact so there will be fuzziness. But the physical pixels on the retina display are supposed to smaller than we can perceive from a normal viewing distance so most people cannot notice it.

Maybe you are sitting closer to the screen than most people do. Maybe you are just perceiving a difference that is not really there. Maybe your text zooming is doing something weird. Or maybe you just have sharper eyes than most and are more sensitive to fuzziness.