pyprocessing is incomplete, nor does it support the re-use of contributed vanilla processing libraries (however neither does processing.js with the exception of toxiclibs, which is in the process of being converted).  With pyprocessing you can use a regular python ide (eg eric-5) for development (with benefit of code completion and other analysis). My guess is pyprocessing will beat processing.py to supporting python-3 (pyglet the underlying graphics engine is almost ready). Also you can use pypy and numpy for pyprocessing to get improved performance. Either way I'm not sure you can leap to javascript, if you are just fed up with java, I'm more of a fan of ruby-processing, that has got good support for both vanilla processing and ruby libraries. In the future coffee-script might be a better alternative, as that really can yield javascript, this is even available in the processing ide, thanks to fjenett.