XML : Localization file: a file for each language or a single file for all languages?

What are the pros/cons of having a single file for all languages and different files for each language?

Single file example

  <localization>      <item id="One">          <English>One</English>          <Portuguese>Um</Portuguese>      </item>      <item id="Two">          <English>Two</English>          <Portuguese>Dois</Portuguese>      </item>  </localization>    

Many files example

  // English.xml  <localization>      <item id="One">One</item>      <item id="Two">Two</item>  </localization>    // Portuguese.xml  <localization>      <item id="One">Um</item>      <item id="Two">Dois</item>  </localization>