SUS304 is the default grade for wine storage and it is the right answer for most projects. It machines and polishes predictably, takes PVD coating evenly and keeps the finished price reasonable.
SUS316 adds molybdenum, which improves resistance to chlorides. That extra resistance matters when the unit sits near salt air, when the cellar is cleaned with chloride-based sanitisers, or when condensation is constant and the surface is rarely dry.
The practical test is location. A rooftop bar within a kilometre of the sea should be built in SUS316 on the external faces. The same cabinet installed inland, in a climate-controlled restaurant, gains nothing from the upgrade except cost.
Mixing the two grades in one project is normal. Many of our hotel orders use SUS316 for exterior panels and wet zones, and SUS304 for internal shelving, brackets and trim.