The folks at Google are making it so that Google Maps and Google Earth are more and more compatible. The latest is the addition of the "My Maps" feature, which allows users to create placemarks, paths, and shapes on a Google Map, just like they can in Google Earth. These placemarks can be saved as a collection, and even exported as a KML file. The placemarks can contain simple HTML, just like in GE.
So let’s recount – Google Maps can import a KML or KMZ file that was created in Google Earth. You can now create KML files in Google Maps. What can one do that the other doesn’t? Google Maps lacks the 3-D topology overlay. Image overlays are also not possible in Google Maps. Tours are an exclusive feature of Google Earth. Google Maps doesn’t have the capability of layering, nor does it support dynamic network files. In short, Google Maps will work for simple GE applications when GE is not available, but won’t do everything Google Earth will do.
Speaking of Google Earth, I was zoomed into the Greenville area and noticed a bunch of little "i"’s on the map, indicating information for that location. I had the "Best of the Google Earth Community" layer enabled. The little "i"’s were placemarks I had submitted as part of my Tour of Greenville KML file. I’m flattered that these were included as the "Best of" layer.