Nested data or join collection?

Hi there I maybe this question was answered before somewhere but i did not find it.

I want to create a structure for the product item and like that the translation content located in different collection and when i need it i just do lookup. Is it a right way or nested collection will be better?

Different collections example:

Product :

    {
            "_id": 1,
            "price": 12,
    }

Content :

        [
                {
                  pid: 1,
                  lang: "ru",
                  title: "Привет" 
                },
                {
                  pid: 1,
                  lang: "en",
                  title: "Hello" 
                },
                {
                  pid: 2,
                  lang: "ru",
                  title: "Пока" 
                },
                {
                  pid: 2,
                  lang: "en",
                  title: "Bye" 
                }
            ]

Connection between through pid for content and _id of product item

Or nested will be better and it avoid using lookup ?

        {
                "_id": 1,
                "price": 12,
                "content": [
                     {
                         "lang": " en",
                         "title": "Hello"
                     },
                    ..........
                ]
        }