How are they different? Flickr KML Feed is extremely fast, shows more photos (up to 250 at once), and highlights the most interesting ones (as determined by Flickr users.) Geofeeder shows fewer photos, though the icon is a thumbnail of the photo. But why choose? Using both network links simultaneously works great.
Notes on the political, social and scientific impact of networked digital maps and geospatial imagery, with a special focus on Google Earth.