Both are great choices. Between the two, the Michelin Xice Xi3 has a bit better dry road grip and quicker steering response while being just as good as the Blizzak WS-70 on packed snow and ice. In loose or deeper snow, the WS-70 has more traction.
You may want to check out the replacement tire for the old WS-70, which is the WS-80.
Winter
http://www.tirerack.com/a.jsp?a=AH8&...nter/index.jsp