nature
world cities: trade liberalisatinon, TNC's, globalisation, technology
mega cities: overurbanisation, agricultural mechanisation, cultural role of cities
character
world cities: finance, culture, economics, trade, goods and services
mega cities: former colonial centres, manfacturing, international divison of labour
spatial distribution
world cities: in developed world, port cities in past, equally dispersed (DOM 3)
mega cities: in developing world, africa, latin america and asia.....