Randomly ordered details to mind when benchmarking a page load time:

• The averaged timing is valid if and only if it is labelled valid.
• The tool relies completely on a properly fired load event to measure when a page has completely loaded.
  • This means if a browser improperly fires the load event, this could lead to incorrect results when comparing two different browsers.
• If comparing two or more blockers:
  • Be sure the benchmarked blocker is the only active extension.
  • To benchmark another blocker, disable the current one, enable the other blocker, then ...
    • Chromium: open the page load speed tool in a new tab.
    • Firefox: restart the browser.
  • Configure them in a similar way.
• Clicking the Benchmark button will launch an automated benchmark session which will end when the average page load time is marked as "valid".
• If you want to bypass the browser cache, open de developer console and check the "disable cache when dev console is opened" setting of your browser.
  • Bypassing the cache can lead to more erratic results though, as the measurements become more sensitive to arbitrary network latency.
• There is a timeout for when a page never completes loading: 30 seconds.
  • The result will be discarded in such case.
• This page load speed tool works only for web pages which accept to be embedded in a frame.
• Since the web page to measure is inside a frame, it may not rendered correctly if you block 3rd-party cookies (a good idea in general).
• This tool can also be used to compare different configurations for the same blocker. For examples:
  uBlock Origin easy mode vs. medium mode.
  • Adblock Plus with "acceptable ads" enabled versus "acceptable ads" disabled.
• When you share the results, you should provide all the information:
  • Browser, version, relevant settings (click-to-play, block 3rd-party cookies, etc.)
  • Blocker, version, filter lists, settings.
  • Which URL was benchmarked.
  • Disclose the whole average result of the benchmark, for example: Average (valid): 832.01 ms (10/13 iterations).
  • Etc.
• Keep in mind uBlock Origin disables pre-fetching by default -- most other blockers do not modify this browser setting.
  • I haven't confirmed so far that this makes a significant difference in page load speed.
• The page load speed tool is completely self-contained, just look at the page source to see how it works.
  • Being self-contained means you can save a local copy onto your computer and launch from there.
  • There is a prototypical feel to the code, I emphasized on it working, not being elegant. I may work more on it as time allows.