I was all about white on black until I realized that I keep being visually fatigued by flipping back and forth into a webpage that was black on white. For me, unless my entire workflow can be white on black, I stick with black on white.
Maybe it's just me but I also find black on white more legible at low brightness display settings as well.
Same with me, though I prefer a very soft grey to full on white. Too many webpages have white backgrounds, and it's painful to flip from a dark editor to go look something up on a glaring white Google.
Maybe it's just me but I also find black on white more legible at low brightness display settings as well.