WebpageTest vs. Google PageSpeed Insights

[nicolesharp100]

Here is a pretty huge difference: https://sandbox.nicolesharp.net/wiki/pro...ox/gallery

WebpageTest says it takes up to 105 seconds (!!!) for the first-view loadtime. But Google PageSpeed Insights says that is "medium" performance with a score of 78%, and actually "good" mobile performance, with a mobile score of 84%.

Looking at the WebpageTest results, it would seem like there are serious performance problems that would make it difficult for people to access the website. But Google PageSpeed Insights says that the website has "medium" to "good" performance, with average performance scores above 75%.

Here is the exact same page hosted by Wikimedia: https://www.mediawiki.org/wiki/user:Nico...ox/gallery

WebpageTest says that the page on MediaWiki.org takes a mere 1 second to load, but Google PageSpeed Insights gives a nearly identical score (only a 1% difference) between the page hosted on MediaWiki.org versus NicoleSharp.net.

So if I only go by the Google PageSpeed Insights score, it would seem that my website performs similarly to Wikimedia's MediaWiki.org. But WebpageTest provides a dramatically different conclusion that is much more worrisome. What might be causing the difference? Should I trust Google over WebpageTest?