I don't think the article is saying: "pypy.js is really fast, why not use it instead of CPython?". It's saying: "Consider using pypy.js on the client, it's c

I don't think the article is saying: "pypy.js is really fast, why not use it instead of CPython?". It's saying: "Consider using pypy.js on the client, it's comparable in performance to native CPython; you consider that fast enough."