Protection Bubble = 100 TerraWatts = 100,000,000 HP
Simple. More money a place has, more power plants , stronger shield, longer time to take down, more people come in, more money, more power plants, even stronger shield.
Capital Cities = Impregnable (but not indestructible Bubbles) Bubbles
Border Outposts = they will have PvPers there 24/7, or someone at least to man some AA guns to defend the base.
