Is spoken English more efficient than other languages?

As a translator, I can assure you that English is no more efficient than other languages.

First, subtitles often miss out whole bits of dialogue and definitely leave out swathes of meaning.

Second, there is no recognized measure of language efficiency. I did a comparative study of cohesion in English and Czech and found that word counts were very unreliable. There is no clear definition of what a word is and most words in any sentence only serve the function of holding the text together. And all languages have different rules. For instance, German or Czech will use more connectives where English will rely on the reader to make the connections in their head. Information density is a very discipline-specific concept. There is loads of 'information' conveyed by any one word that would not be captured by this notion.

Third, many bilingual speakers will tell you that there are certainly areas in which one language feels more expressive than another. So it's true that English adjective chain formation makes saying some things much easier (kind of like German word formation). But a language like Czech can express many things more efficiently thanks to its aspect or case markings. So overall, all languages are probably equally efficient.