If you're a True Winter then your best white is the purest, most intense of all. Pure white looks incredibly harsh on most people. Other seasons' versions are mixed with yellow or grey or something else. Only True Winter can look completely at ease in this colour.
Keep in mind that really shiny fabrics usually look great on True Winters. Light seems to reflect off the surface and interesting icy colours appear in the folds and shadows of the garment. The effect makes a True Winter ethereal and radiant but try putting this dress on another season and it will just look tacky.
A brief endnote: pure white is actually pretty edgy. When most of us imagine sweet white dresses with ribbons and lace and cornfields and romance, think again and look carefully. Almost always the "white" has been softened with a little colour blending.