After posting on inkscape-user and increasing the sample size, it seems to me that there is a clear consensus in favor of the new style.
Bulia wrote:
There's no need to argue. Ben, you can continue working on the new icon set, and when you are ready we will ship your icons.svg alongside the old one, so people can choose whichever they like. Trent, the same for you: you are welcome to develop a set of icons that work best for your black background, and we'll ship them also. When there's at least one complete set besides the old one, we can make a preference with a UI to choose one of them on load.
The real issue is whose icons will be the defaults. Since most people seem to like mine better than yours, I think mine should be the defaults.
I would like to request a clear decision on this from the core developers before I invest a lot more time on the icons.