I went with the widest front tire to complement the rear and afford maximum floatation in mud, snow and sand. Others could argue a narrower front tire can cut deeper and thus track better. Opinions will vary wildly but the actual difference may be fairly subtle depending on your riding conditions.
Wider tire will weigh a bit more and thus subtly affect performance. If you need to loft aspen logs, wheelie, or maximize acceleration then get a skinny tire.