I wrote a game renderer with pygame, its >10x faster in pypy... it's voxels (in the comanche sense).

That's just an anecdote but obviously you should check your use case and find what tool is best suited for your project. There is no magic cure-all, but in my experience pypy comes close.

I'm pretty confident it's also going to be a magic speed boost for a decent size web app I work on, but it remains to be tested with this particular app so I'll check it out... The most bulletproof way to find out what's faster is to test it.