One comment, iperf does not utilize the disk for testing. so slow disks will not slow it down. You can also use -P with a number to speed it up depending on how many cores it has.
As with most people it depends on the job. I tend to prefer bash if it's 10s of lines or less, especially if it's connecting several other utilities together to form one.
For bash, I disagree with one statement:
Piping ("|") CLI utilities like sed, awk, grep, etc. can slow its performance
It's the opposite... Piping CLI utilities can speed its performance as each step in the pipeline is parallelized and so it can be working on multiple portions at the same time, putting those multiple cores to use. This is very effective when doing several layers or processing through a TB file.
Python lacks support for true multithreading, although it can do similar to multiprocess as bash, but the | in bash makes it far easier than python for those tasks that lend tend themself to being run in a pipeline.