More features : Offline capabilities and hundreds of predefined sentences.
In Qtranslator, you can BYOD : build your own dictionary ! Type a sentence, have it translated to the language of choice and add it to your favorites.
Later, you can lookup your favorite without the need for an active internet connection to do the translation.
QTranslator also includes a few hundred predefined common English sentences, that you can use as a starting point for your translations.