Generally screenshots can hardly do programming fonts justice. You have to load them into your editor and try them out on familar code.
Most of the fonts showcased on that page look perfectly fine to me from the images. I only learned that I can't bear an anti-aliased font and about my various gripes with the other fixed contenders because I once went and tried all of them for at least a few hours each.
I've found that some fonts look much better as light text on dark backgrounds, or vice-versa. I use terminus (http://shenani.gen.nz/~scott/img/terminus-sample.png), but something about it doesn't look right to me on a light background.
But I, too, noticed the difference and I don't think it's just subjective. Black-on-white is generally easier on my eye in the short-term but for the long-term (e.g. coding sessions) I strongly prefer white-on-black because staring at a mostly white screen for extended periods of time makes me dizzy.