Choosing Java vs Python on Google App Engine

Question

Currently Google App Engine supports both Python & Java. Java support is less mature. However, Java seems to have a longer list of libraries and especially support for J

Answer 1

There's also project Unladen Swallow, which is apparently Google-funded if not Google-owned. They're trying to implement a LLVM-based backend for Python 2.6.1 bytecode, so they can use a JIT and various nice native code/GC/multi-core optimisations. (Nice quote: "We aspire to do no original work, instead using as much of the last 30 years of research as possible.") They're looking for a 5x speed-up to CPython.

Of course this doesn't answer your immediate question, but points towards a "closing of the gap" (if any) in the future (hopefully).