I've no experience of Worldwind but Cesium and ViziCities both use WebGL and both display the same kind of data. Cesium is built around the concept of a round, globe-like representation of the world whereas ViziCities is a flat representation of the world. ViziCities is arguably simpler to use and simpler in functionality, whereas Cesium is built with scientific and incredibly accurate scientific data visualisation in mind (eg. satellite positioning).