I love the look of black and white bathrooms. They tend to have a style that is both retro and contemporary at the same time. Especially when the floor is tiled with hexagonal tiles. If you also love that look,then a black cabinet would probably look better than a white one. Since white bathroom furnishings are so common, they don’t tend to make much of an impact, decor-wise. Black is a bolder choice that gets noticed.
Two nice examples – I love the muted gloss paint:
Black over-the-toilet storage pictured:
Left: Zenith Products Matte Black Spacesaver
Right: Elegant Home Fashions 7619 Madison Avenue Wall Cabinet Dark Espresso