Flickr Vs Picasa

Here is an article comparing Flickr and Picasa, and the winner is "Flickr".
http://labnol.blogspot.com/2006/12/picasa-web-albums-vs-flickr-which.html

Also, note that there are some tools available for downloading pictures from Flickr. Downloadr is the tool for Windows only, Size: ~300kb zip. Below is an article about the same.
http://labnol.blogspot.com/2007/04/download-multiple-flickr-pictures-in.html