The unladden-swallow page says they're using the LLVM JIT compiler in order to be able to compile Python / bits of Python to machine code. So it's less about c

The unladden-swallow page says they're using the LLVM JIT compiler in order to be able to compile Python / bits of Python to machine code. So it's less about choosing a VM from LLVM / Parrot / JVM / etc and more about using a feature of LLVM to get a speedup.