What's the difference between Language Switcher and Translation block?
Deep in this old thread, "Looking for internationalization use cases and application feedback" - http://drupal.org/node/88417 - a user wrote:
I'm not sure what I did wrong but the Language Switcher block failed to work on mine site. I've to use Translation block instead
Good enough for me to start out with Translation as the block, since they look identical anyway...