I think dark background because it has the following advantages:
1. Eye fatigue from video glare is reduced
2. Flicker problems (if they exist) are reduced by dark backgrounds
3. Some medical conditions (e.g. photophobia) are less aggravated by dark backgrounds
4. Colours, when used to convey information like syntax highlighting, might be easier to notice against a dark background
5. Less blue light could mean less disruption to the body’s sleep cycle if using the display in the evening
6. On some displays, dark colours save electricity and since darker displays are more suitable for use in dimly-lit rooms, the lighting can take less electricity too
7. Defective pixels that are permanently dark can cause less confusion if the background is darkand if, after an accident, the display still works but a digitiser (“touch”) or other layer in front of it is cracked, then this might be less noticeable against a dark background, hence allowing more time between repairs or replacements
8. If the display is surrounded by a dark border, then bright text can touch its very edge without causing confusion, unlike dark text which may need a margin (dark lines running along a black edge won’t stand out), therefore light text on a dark background can make better use of space during full-screen presentations etc.