Keep your site performance up
As Josetta relies only on Joomla! core content and translation system, you get an added benefit: speed
When using third-party multilingual extensions to manage and display translations on the front-end of your site, additional database queries are required to retrieve each translated element such as articles, but also menu items, categories titles, etc.
This can quickly become noticeable to your users, and also to search engines. At best you'll need a bigger server or more optimization work to compensate. At worse, if nothing is done, you could have a less competitive position.
With Josetta, you get no overhead at all, because Josetta is not used to display content to visitors, only to manage and translate it.