I'd suggest to use .get() if you know what the appropriate selector for your element is. If you'd use a simple .contains('Facebook') and there is another element which contains the word Facebook, you're risking cypress will match that element. I guess if several elements match, it depends on the order in the DOM tree. In such case, you'd need to be sure about the order of the elements and use .first() or .last() commands (https://docs.cypress.io/api/commands/first.html)
Using .get() is conditioned by you knowing the selector(tag, class, attributes etc). It's more decisive and selects the exact element you specify with the selector. Use get and avoid the risk of matching another element with the same text.
You can read more on the usage of those two here:
In your particular case, if there was a div above your list (e.g. <div> Facebook is amazing!</div>) cy.contains('facebook') would match it and the attribute you're looking for would probably be different and therefore would your test fail.