Edit: the particular quote I objected to was edited out by parent.

I object to "all the dynamicness of the rest of the JS is what V8 excels at". V8 excels at a subset of dynamic JavaScript (namely those benefit from Crankshaft) and is not very good outside of the subset.

Typescript benchmark included in Octane benchmark suite is a good example. In Google's own words: "This test measures the time TypeScript takes to compile itself and is a proxy of how well a VM handles complex and sizable Javascript applications".

In particular, Crankshaft is not effective for this benchmark. (Check yourself by running it with Crankshaft disabled: the score actually improves because you save compilation effort.) And as you can check yourself or check on AreWeFastYet, JavaScriptCore beats V8 by 2x on this benchmark.

I admit Crankshaft subset of JavaScript is large and interesting (certainly compared to asm.js subset) but it is not true that V8 excels at dynamic JavaScript, for sufficiently large value of dynamic. JavaScriptCore does.