The two snow areas in Pokemon X and Y stood out to me more than any other area in the game, mostly because of the utterly fantastic soundtracks that accompany these areas. The Frost Cavern is absolutely majestic and beautiful, and Snowbelle could easily be the best town in the game.
If I were more acquainted with the Johto region, I may have picked the Ice Path due to it taking you to one of the more beautiful towns in the region. As it stands, however, I'm not, and nor am I saying the snow in Sinnoh was great because it definitely wasn't. The snow from Sinnoh makes me never want to go back.
Pokémon X & Y has the best patches of snow in any Pokémon game so far. And the best soundtrack. I will literally find myself sitting just inside the Frost Cavern, listening to the OST while my character turns into a cute frozen popsicle.