I was thinking the same thing, Al1943. If the snow is a thin layer on top of pavement or gravel some other hard surface then I prefer to run narrower (like 28 - 35mm) high pressure tires to running wide mtb style tires at low pressure... and if I only have wide tires I run them at top pressure or higher. High pressure allows the tire to cut down through the snow and contact the hard surface below.

If I am riding on deep or packed snow where I have no chance of staying in contact with the ground underneath I use wider softer tires as this will provide 'flotation' on top of the snow.

My current winter bike has 35mm rear tire and a 40mm wide studded tire on the front... which is a middle width and so goes against my advice.