ya mark, thats what i did... i picked up a set of stock toyota ones (same bolt pattern) and then that opened up a world of options for tires... and they also have 15's and 16's.
you are incorrect about the cutting billy, a narrower tire has less likelyhood to 'float' on the snow (think about a snowboard at high speed and skii's at high speed, the board floats much better). but you ARE correct about the contact area also, they give more weight per cubic inch and therefore have less likelyhood to slide.