Yeah, I'm not sure you can say anything meaningful about eye strain and readability without accounting for room lighting, glare, and other reflective surfaces and distractions. If I'm in a dark room with a bright screen, it's almost physically painful to stare at the screen. I have to turn the brightness way down, and then I lose contrast and have to strain even more. In an office with horrible flourescent lighting, highly-reflective white walls and surfaces, metallic accents reflecting light into my peripheral vision, reflective monitors (Apple displays are the worst), and eyeglasses, I'm practically blinded. The last thing I want is glaring white light from my application windows.

There are things other than black-on-white and the inverse. I've been using Solarized dark where possible for years, especially in code windows. White-on-black is horrible, but pastel colors on a slate blue-gray background is the most comfortable option for me.