>The one that is so fast because it compiles in JIT
That's true for all modern JS engines (JavaScriptCore, Edge, SpiderMonkey, v8) and has been for several years (almost a decade).
But only after V8; before that, JS performance had no priority in browsers.
That's a common mistake, but JITs in WebKit and Gecko came out at around the same time as v8. Their development began before v8 launched.
edit: For example, see the dates on Wikipedia, v8 launched September 2008, and WebKit's Nitro (SFX) JIT launched in the same month.
Nope.
In fact Mozilla was somewhat earlier to come up with their JIT-ed JS engine, then Google (v8), then Apple (JSC), but all went live with an insignificant time difference between them (all within a few months in 2008).
(Insignificant since the respective companies have already been working on them simultaneously for years -- so going live was mostly based on who wrapped up first, bugs be damned, not on some unique innovation that others later copied).
Also for the worse: the one that lets us include 10Mb of js in a browser.