I think that we can agree that insulating the top keeps heat in. A ceiling that is kept relatively warmer will be subject to less or no condensation to drip on the cluster. Some air exchange is necessary to maintain oxygen and carbon dioxide levels. Excess air exchange is the enemy of heat retention. Bees either need to fly to eliminate or are inclined to do so. If you have a 2 or 3 deep colony with only bottom entrance that distance is an issue.
If you have the top of a colony air tight and well insulated, ice and snow conditions and/or dead bees that thoroughly block a bottom only entrance will kill your bees.
Different local weather conditions will alter the relative importance of these issues so it is up to you to decide which ones apply more to you.