As a principle, you should use 敬語(丁寧語） almost always in any situation. (The "敬語" mentioned here refers to "です／ます体", not "でございます体".) *********************** Please see. ”Don't speak a casual form called ”タメ口", to others" https://www.italki.com/question/431321 https://www.italki.com/question/427450 *********************** However using "敬語" has pros and cons. While pros is, of course, that you can show respect to others, cons is to reduce the effectivity of communication. Too much using of "敬語" would make redundant and unclear what you say because "敬語" are words for mood and not for information exchange. In other words, "敬語" does not have information value to the audience. I think the most important point is that the audience understand that at least you have "INTENTION" to show respect to them. Once it is achieved, then what matters most is your presentation itself, interesting or not. FYI : TED presentation by Japanese people in Japanese. https://www.keikawakita.com/entry/201611ted-japanese

You should speak in 敬語　(敬語= collective term for 謙譲語、尊敬語、丁寧語） The difference between 尊敬語 and 謙譲語 and 丁寧語　is: 謙譲語(humble speech) is the term used for the words used to humbly refer to your own actions (when speaking with a person higher than you in the hierarchy) 尊敬語 (respectful speech) is the term used for the words used when respectfully referring to others actions (when speaking with a person higher than you in the hierarchy) 丁寧語 is 「ます・です」 They go hand in hand if you know what I mean :) PS: I think many Japanese are happy even if you only use ます・です Especially since you are a foreigner and because perfect 敬語 is very difficult even for native Japanese speakers.

Japanese business presentation should be like this みなさまがご存じのように、 casual Japanese みなさんが知ってるように、 in English As everyone knows