GTranslate exists from 2008 and is very popular while SEF Translate is relatively new.
You can use our product on any site instead of just Joomla.
Our product allows to edit the translations right on place. You can watch the tour to see how it works: https://gtranslate.io/#!/tour
It doesn't push you to buy Google Translate API key to use the Google Translate translations while SEF Translate offers only Bing Translations for free.
GTranslate caches translated texts instead of caching the whole translated page. Which saves disk space and there is no need to re-translate the page when something changes on it.
We also send updates free of charge offer free support and installation.