[pansa2]

> python - as a language - is way more "dynamic" than javascript

Very true, but IMO the existence of PyPy proves that this doesn't necessarily prevent a fast implementation. I think the reason for CPython's poor performance must be your other point:

> the ffi-bindings of python [...] limit how freely the internals can be changed

[eru]

> Very true, but IMO the existence of PyPy proves that this doesn't necessarily prevent a fast implementation.

PyPy pays for this by having slower C interaction.