Here we go. Not only is there a battle for the best search engine, mapping software, free email, toolbar, and custom portal. We now have a battle for the best earth imaging program. Google has recently added overlay (hybrid) sites to show sat pictures and roads (http://maps.google.com) and now we have Microsoft playing in the mapping / sat images game. Not only with terraserver, but now Microsoft, with their MSN Virtual Earth (virtualearth.msn.com).
I have not done a full comparison of the two yet. However, I can tell you that my personal favorite is the Google solution. I have been playing with the customization of the google maps application for a while. I like the feel and the way you can modify it.
With that said, there is also an easy way to customize virtual earth with the use of .NET. I am a .NET programmer at work and the ease of intergration and use for anything .NET will be easy for me. So before I make any remarks I would like to try the new Virtual Earth and create my own opinion.