The following is the result of prototyping some automated perfomance tests with puppeteer. The same template and template data is used in the lit-transformer demo and mustache demo, which look like this. The results are the mean value of 100 runs.
The first data point (initial render) is taken after the page is fully loaded. The second (changed data) and third (changed data back) is measured after clicking the button to change the data in the next requestIdleCallback.
As you can see ScriptDuration and LayoutDuration is pretty much the same. But in RecalcStyleDuration you can see the advantage of re-rendering only the insertion points, as it is done by lit-html, over re-rendering complete innerHTML, as done by mustache.