It depends on the goal of the script. I tend to rewrite complicated shell scripts in Ruby, but working with subprocesses in Ruby is terrible, so those scripts

It depends on the goal of the script. I tend to rewrite complicated shell scripts in Ruby, but working with subprocesses in Ruby is terrible, so those scripts are destined to end in `.sh` forever. bash has a very specific purpose where it excels over scripting languages like Python and Ruby: wiring input and output and communicating with subprocesses.