The benchmark at the bottom showing how far behind Firefox has fallen on JS performance is pretty telling. It confirms my own recent observation that Firefox is at least 3-6 times slower in practice for the particular app I'm working on.
A vendor is always the fastest when they roll out a new benchmark. It's disingenuous to suggest a browser is '3-6x slower' based on a score on one benchmark, when all the vendors actively compete on and optimize against a large set of benchmarks, and compare each others' performance numbers on individual tests to understand engine weaknesses/strengths. fwiw, Chrome, Firefox and Safari have all been fairly competitive…
It's enough to make the startup feel slow (3-4 seconds of being unresponsive) and things like animations and drag and drop features to feel janky. Running a non-minified build (about 20MB of JS, minifies to about 1MB) also completely murders Firefox reducing it to a slideshow, making Firefox unusable for development, while Chrome works just fine.