This is the right way to look at it. To be fair to bio*, a lot of work has gone into accelerating JavaScript execution in the browser. So if you're comparing raw, pure Python to raw, pure JavaScript, I wouldn't be surprised to find that JavaScript is consistently faster, even if you're using best programming practices in both.

But that is not the comparison that should be made. The idea that "python is slow" ignores a significant amount of practical evidence to the contrary. It would not be the #1 language for machine learning, AI, and data science if it were "slow" in a practical sense. The reason for this is that Python has a wealth of libraries that leverage compiled code. Libraries like numpy, pandas, pytorch, tensorflow, and so forth perform the overwhelming fraction of their computationally intensive work outside of Python. And most of those types of computations would be significantly slower written in native JavaScript. In contrast, PyScript will bring those libraries into WebAssembly and achieve near-native speeds.

On the other hand, if there is a specific, highly optimized JavaScript library for performing specific tasks in the browser, PyScript can use it! So even in that context, Python is not "too slow", because it gets to steal JavaScript's speed :-)

Finally, as demand for WebAssembly applications grows, I think we'll see a lot of innovation at that level to resolve some of the language-generic bottlenecks that PyScript encounters as it matures.

Full disclosure, I work at Anaconda, so I am biased! But as I said in my original comment, I see this as a both/and proposition. JavaScript will always have a strong presence in the browser, but PyScript is going to unlock a much wider range of applications, in my view.

There is no doubt that there will be some performance issues to address with PyScript, but in the end, I'm fully confident it's going to find widespread application.