I am working on one website, to optimize the performance.
I had, according to Pagespeed Insights (https://developers.google.com/speed/pagespeed/insights/?) a Server Response time of 1.7s.
After some work, Lighthouse (embedded in Chrome) gives me a Server Response time of 200ms, my page is noticeably faster. But Pagespeed insights still gives me results in the 1.5s range.
Which one should I trust?
Google PageSpeed uses a “combo” of lab and real-world data, whereas Lighthouse uses lab data only to build its report. Since lighthouse is integrated into PSI for sake of consistency you should trust PSI over just lab data.