Nasa World Wind and Google Earth are the most popular publicly available virtual earth software. Each one has it's own strengths and weaknesses. You should select the appropriate program depending on what you need to get.World Wind is mostly based on Landsat7 imagery which are consistence throughout the world. Google Earth provides images with very good resolution but sometimes they are not consistent. For example, the Mahaweli river takes a mysterious bend just after the Katugasthota town and the adjacent images are very much differ in resolution and aligning. It makes a big doubt on the accuracy of the system.
But if you want to locate a place in Colombo World Wind can't help you with its low resolution images but Google Earth will show even markings in your tennis court.
I like the smooth motion of World Wind and it's 3D views. Even when you move over the tiles without tilting, you can see the 3D nature of the terrain. The colors also visually appealing than in the Google Earth.
World Wind has a very rich geocode database. If you search for a remote village in Sri Lanka, the chances are very little that you failed to get it. Also it provides several layers that you can switch to and they are in different resolutions and contains different data.
Also you can see the real time weather with animation in World Wind and some scientific visualizations.
Although World Wind provides USGS maps as a layer they are way behind features of Google Maps. Although Google Maps is a different product it is superior with its API and the coverage. Recently Google Maps added geocodes for entire India so that the detail maps are available for any place. We can expect Google will soon release maps for Sri Lanka.
There are lot of interesting things in both World Wind and Google Earth. Each will provide more and more features in the future. But more than anything, World Wind is Open Source.
