Showers with a level entry wet room are becoming very popular, especially due to improvements in waterproofing systems and prefabricated components.
Best practice requires a waterproofing material to cover the walls and floor of the shower area, that are then covered with tile.
Tile
Tiles are generally waterproof, so larger surface areas of grout are less waterproof.
Grout is used to fill gaps between tiles, but this material is generally porous.
Thus small mosaic tiles offer less of a defense than large format tiles but ceramic, glass and porcelain tiles are inherently very slippery when wet.
For use on floors can be made more slip resistant either by using very small tiles so that the grout lines acts as grooves or by imprinting a contour pattern onto the face of the tile.
Ceramic tiles typically have a glazed upper surface and when that become scratched or pitted the tile looks worn, where as the same amount of wear on stone tiles won't show or will be less noticeable.