I've read that, while the science/usability research is largely non-committal about which is better, it seems that black on white or similar makes your pupils d

I've read that, while the science/usability research is largely non-committal about which is better, it seems that black on white or similar makes your pupils dilate much less and therefore is easier for working for longer periods (less eyestrain). Though, as you say, I think you also really do need a well lit area to take advantage; super bright in a dark room isn't very good.