For a server-side plug-in:
- Install your own local copy of WP/MT/Drupal
- Download Zemanta plug-in
- Install plug-in in your WP/MT/Drupal directory
- Turn Zemanta "ON" in the admin interface
- Start writing and experience Zemanta!






There is no difference in the Zemanta experience, you get the same functionality.
If you own a self-hosted blog then install the server-side plugin, if you are unsure, install the browser extension.