Cython is really about writing C code in a Python like style to create Python extensions. This adds additional complexities in debugging (can't step through in your IDE seamlessly), building and distributing. The trade-off is acceptable in specific cases, but quite clunky otherwise. I am not eager to write anything substantial in it since tool support is not super. Cython is a neat hack. But a better example of using a statically typed native code for performance and a dynamically typed language for productivity is Java + Groovy.
Ultimately however, the language choice boils down to it's eco-system, the point that Miguel was stressing. I pick the language based on whatever community has the libraries and experience for the kind of problem I am solving, even if the language and performance are not the best fit. Python is great for my scientific projects (lots of easy-to-use libraries, quick prototyping). But I am yet to see proper mature equivalents with tooling for things like ZK, and Eclipse RCP on the Python VM.