The old dilemma third party service or doing your own thing. As devs we tend to create our own solution, but I can tell you, focus on your core business.
My guess is your core business has nothing to do translation, localization, ... so I would recommend using a SAAS based solution.
Services bring you a lot of features and stability you otherwise have to do on your own: Syntax Checking, Keeping track of the translation texts (status, review process, ...), char count (for external translators), context (WYSIWYT) and so on.
As the founder of lingohub.com
I am clearly biased, but we ourselves use many other services as well because making software translation as easy as possible is our core business. Not issue tracking (JIRA), repo hosting (Github), Continues Integration (Codeship), ...
And the good thing, there is no vendor lock-in, you always have your resource file. If you are not happy with a service, you can leave at any time.
If you have questions about lingohub, just contact helmut - at - lingohub . com