Ranked in these QuestionsQuestion Ranking
Pro CLI tool
Transifex has a CLI integration tool for managing large amounts of text.
Pro Integration with CI tools
Transifex supports CI tools like Jenkins or Bamboo.
Pro Many supported document formats
Supports gettext, yaml, json, magento csv files, and many more formats.
Con Outsources translation to other agencies
While not a bad thing, or something that the customer should care, but it may influence the quality of translations since Transifex themselves don't have direct control on the translation process.