Good snow tires on all wheels, such as Blizzack's or other manufacturer's equivalents are really beneficial in snowy/icy conditions. Problem is if you don't drive in cold conditions the tire life diminishes. AWD and much broader array of all season tires are even better in snowy/icy conditions.
I use Michelin XGTV4 on my 4-matic and logged about 9K miles in snow country last ski season and the combination does well in some fairly horrific conditions. I've used them for about a third that so far this season and they continue to perform well.