Ranked in these QuestionsQuestion Ranking
Pro Many supported document formats
Supports gettext, yaml, json, magento csv files, and many more formats.
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.
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.