In a vacuum I think you could argue that the black socks are better strictly from a design perspective, at least is more consistent. However, as a B's fan, I hate the black socks. They had an unusual look that differentiated them from the Pens or some random minor league team. I do agree that a tweak or two to the stripes on the yellow socks could be an improvement.
Interesting that they got through the BFBS uniform phase with yellow socks and just as the fad is about done, they switch to black. I hope I'm wrong, but I have a feeling that they are going to be wearing black socks for a while.