White mosaic tiles have a completely different character to a standard tile, made up of small pieces mounted together on a sheet rather than laid individually. That sheet backing is what gives mosaic its real advantage: it can flex slightly, which makes it one of the few tile formats properly suited to curved walls, arches, and other rounded or recessed surfaces that a flat, rigid tile could never wrap around.
Because there are so many more grout lines than on a standard tile, the grout colour becomes a real design decision in its own right: a contrasting shade will accentuate every piece and give the surface a more graphic, patterned look, while a matching grout lets the white read as one continuous, textural surface. Installation is straightforward too, since you are fixing and grouting the whole sheet at once rather than working tile by tile.