According to Jython's (a little dated) FAQ <https://wiki.python.org/jython/JythonFaq/GeneralInfo>, "Jython is approximately as fast as CPython--sometimes faster, sometimes slower. Because most JVMs--certainly the fastest ones--do long running, hot code will run faster over time."

PyPy aims to be (and is in many cases) faster than CPython.

The advantage with Jython isn't a performance one: it's the ability to call Java code directly.