From what i've heard (2 sources - tirerack.com and discount tire), a wider tire will have a tendency to plow through the snow rather than "slice" through it. This meaning that the rotation of the tire is less efficient and more difficult. I can't really see an inch or two making a difference in this example. I mean unless you are comparing 375's to like 215's. The guy at discount tire said that a winter tire would give you better performance if it was thinner, but he said on an all season/all terrain tire wider would be better, especially on a truck. I think for moving through the snow a thinner tire would be better, but for keeping traction in snowy slippery conditions, i'd rather have more rubber on the road.