Comment by CharlesW

> A dithered image almost certainly beats a non-dithered JPEG compressed image in terms of file size, because you can JPEG compress the dithered image. Thus, if you like the look of a dithered image, you get file size reduction as a bonus.

That's backwards. Dithering (and simulated halftoning, as in this case) adds detail/noise, making images harder to compress efficiently.