Looking at the results at the moment, it appears as if the preference has flipped round since 2010 or so... Can anyone who posted here earlier say why they prefer black over blue, other than it being what's "in fashion" or "different to what their parents wore"?
I find that mid wash blue jeans go well with both black and white shirts, along with a wide range of light-mid colour shirts, whereas black jeans only go well with certain muted colours, and I find this colour scheme, which has pretty much dominated fashionable clothing for the past 5-6 years, to be drab looking, as I said earlier.