English has become the default language in business. I would recommend anyone designing a deck for an external audience to use that language for the slides, but still present in your local language if that works for the people you are speaking to.
- Your business might be dealing with local contacts at the moment, but that could change in the future.
- Building on this. Increasingly, people use remote talent for certain tasks, having your documents in English helps these people getting on board
- People have gotten used to English text in advertising. A presentation in Hebrew (weird characters, written right-to-left, even looks strange to Hebrew speaking investor audience here in Tel Aviv.)
And there is another benefit. If you slides are in English, but you need to tell. your story in another language, you cannot easily fall back to just reading the text on your slides. Instead, you need to make it your own story.