After my standard introduction and opening joke in Vietnamese ("I'm learning to speak Vietnamese, but often Vietnamese people have no idea what I'm saying" spoken in Vietnamese, always gets a big laugh) I began speaking English. But then I started peppering my talk with Vietnamese phrases and a sentence here and there. Then I switched entirely to Vietnamese, relying on the translator only for a few words or phrases. I surprised myself and completed about 70% of the 15 minute speech in Vietnamese.
I thought this was pretty cool.
After the event, though, one of the major feedbacks was "It would have been better if you had spoken in English."
I asked if anyone had trouble understanding me. "No, they understood everything you said."
Once I thought about it, it made sense for two big reasons. The first: A lot of peole in the room had spent years learning English. When they see an American on stage they expect to hear English. And all those years of work paying off by understanding a native speaker at a professional event is a good feeling.
The second: People said that I was more passionate when I spoke English. I buy it. Speaking English requires zero effort, whereas speaking tonal Vietnamese requires a big chunk of my brain's attention to get it right (internal dialogue: "oh boy make sure you use dấu nặng and not dấu hỏi here").
So, I'm gonna stick to English in future presentations. I'm not going to stop working on my tiếng Việt though.