I was once a firm believer of 18's for winters. However, as of the last 2 winter seasons, i run 20's non-staggered on dedicated snows w/ 30mm rear spacers. I may keep the 10mm up front to test out, this season. They've held up quite well even on ski trips...some of which include a bit of off-road and inclines of ~30-35% up an unplowed driveway.

Several years ago it was a challenge to locate snow tires in 20's for my X...but with the release of more performance-oriented suv/sav's, i'm finding more available variety.

At the end of day...decide on what's best & safest for your situation. Happy hunting & motoring