Galileo's compartmentalized layout benefits protracted defensive stands in the unlikely event of an attack.
Because Complex is a medium sized map you can see most of the map whereever you are, but that can change since there is a lot of cover all around the map. The roof of the center building can be used as a sniping position since it can see most of the map. This is also where most of the fighting is going to happen since its in the center of the map.
During Flood, the center building and one of the towers near the shore is where people hold out during Flood since it has a great vantage point and there are a lot of choke points for the Flood to funnel through. This also makes it a good idea to wait for survivors near this point and eliminate them as they come.