as other people have mentioned, you're going to get lots of different opinions with this question. so let me add mine:
during the summer, when i think the trails are a bit more sandy and soft, i run a larger volume tire with a pretty low pressure. in the winter, a smaller volume tire with (still) a fairly low pressure - i find myself more worried at keeping my PSI around the 30lbs mark during cold months and try to put air in my tires as little as possible during the summer.
to me, tire tread depends on the type of riding one might want to do while encountering specific conditions. this would also depend on how much traveling you do with your bike - a tire tread perfect for riding at UWF might be something completely different than a tire that works well over a myriad of terrain, and vice versa.