> Also why should I pick this over cython, pythran or numba?

One scenario would be that there is code already written in Julia, which you would like to expose to a broader audience. Although overall Julia's ecosystem is smaller than Python's, there are some niches within which it is highly developed. Library code accessible from the alternatives you listed is mainly limited to existing Python and C code. See the demo with `ParallelKMeans.jl`, which wraps a high performance Julia library performing K-means clustering, which could be a useful addition to the Python ecosystem.

Another scenario is that you want to write some custom code which makes use of the Julia ecosystem and then expose it to Python.