2 deep hive bodies gives the queen more laying room and the colony more room in which to store the year's food supply. We need to remember the goal is to bring the colony through the winter in the strongest possible condition, not just to bring it through the winter. Leading up to the spring flow a good queen will have 14 to 16 frames with brood in a double deep, she can't lay that much in 1 deep and a medium.
Square inches of comb space can be met by other hive configurations but 2 deeps are good if weight is not a problem. Also remember the comb used for brood comb should be the best comb possible, the queen can't lay to her full potential in poorly drawn comb.
