Hey, I think you’re totally right to challenge a statistic when it looks questionable. Censuswide didn’t release the full data publicly, and the survey was commissioned by the Ghostery ad blocker, so there’s reason to suspect that the data is biased.
I trust the YouGov data more, since YouGov is also a credible pollster and the data is being provided as market research data for businesses. However, since I don’t subscribe to their data service, I don’t have details of the methodology here, either.
Between these two options DuckDuckGo Browser is at least free and open source, while Vivaldi is closed source, which makes DuckDuckGo Browser the better choice.
Firefox and its forks are better than both. Firefox’s Gecko engine is independent of Google and Apple, while Vivaldi uses Google’s Blink engine and DuckDuckGo Browser uses either Blink or Apple’s WebKit engine depending on platform.