As usual, "it depends." If you have complex logic, it's generally much cleaner to implement in python.

(If you told me I had to rewrite a working Python script in shell, I'd probably think you were joking. Talk about nonsense.)

'It depends..' is a quagmire for the unwary.

My route is to make a good rule about writing python with more than 'n' os., subprocess. and *.Popen calls automatically requiring shell script counterparts in case we find your need to pythonize unsafe, unreadable and slow|broken|buggy.

There are obviously programs that are better written as a shell script, no denying it! I'm just saying use the best tool for the job. If you're writing complex logic in a shell script, you're probably barking up the wrong tree. Likewise, if all you're doing is calling external programs from python, you're probably doing it wrong.