Depending on the snow conditions, i would stay clear of the Northern side of the mountain, as the Miners, PYG and llanberis paths, are very susceptible to ice.
By far the safest route in the full throws of winter, is the Snowdon Ranger path near Bettws Garmon.
The path has very few locations that allow a build up of snow, as virtually the entire path is exposed to the prevailing wind that blows most of the snow away, so its possibly the safest route in winter..
Even after the lengthy repairs made years ago, the Zig Zags where both Miners and PYG tracks meet, is still a massive hazard for the build up of ice.
Also, the steep path above Clogwyn Station adjacent to Clogwyn Du Arddu, is notorious for ice during hard winters, and has claimed many a life.
If you must climb Snowdon in the white stuff, then the Snowdon Ranger offers possibly the safest route, but it all depends on the conditions and strength of the wind.