A localization department within your company — in-house specialists who work exclusively with you and can get completely immersed in the project.

Benefits: you can control the process from start to finish, and you won't have to give project information to third parties.

Downsides: this puts a bigger load on HR, and it can be expensive to maintain a team.

You'll work with professionals who are highly knowledgeable about the localization process, and have most likely worked on projects relevant to your project before. Your task is to produce a thorough project spec sheet, and the team will take care of the rest.

Benefits: this costs less than having your own department, you can order independent testing at any time, and the vendors take on all the responsibility.

Downsides: you're giving information to third parties, deadlines and costs can increase due to force majeure situations, and you don't have complete control over the process.

You'll be interacting with individual experts for each language pair. Their task is completing translations into the target language before the deadline you set, while maintaining your project's style.

Benefits: a wide variety of experts are available at agreeable prices. You'll just need a localization manager to control the process.

Downsides: proven specialists tend to cost quite a lot, and it can be difficult to control deadlines and quality — you may need editors.