White background and blue light aren't a good match for your eyes, especially during the night. You can tweak your screen settings or wear protective glasses to tackle this issue. However, those blue cut lenses can be a pretty expensive solution unless you're already wearing glasses. I guess that this depends on the county you're living in, and from what I've seen the prices vary greatly between Europe and USA.
I also prefer the dark background since syntax highlighting looks kind of better. ¯_(ツ)_/¯