Snow performance depends more on rubber compound and tread design than it does on width. Older designs of winter tires drove from the edges (the lugs) and so it was important to get a narrower tire if possible. Modern winter tires with soft compounds have sipes across the whole tread width, and so drive from the full width.

Excessive width still matters in that a tire tends to have to climb up continually in deep snow, it just isn't as critical as it used to be.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue