although see this comment from the replies: https://news.ycombinator.com/item?id=18701430
First, I can find nowhere that Chrome claimed to have better video-watching battery life (in fact, popular tech sites mention improving but still worse).
Second, the only dip I can find in the public Edge battery life tests was
April 2017 - 12.5 hours
Dec 2017 - 16 hours
May 2018 - 14.3 hours
vs Chrome's 9.3, 13.5, and 12.5 hours. Which means whatever happened last spring, Chrome also dipped."