Use the shell only if your script is mostly about calling other programs and filtering and redirecting their output. That's what the syntax of these languages is optimised for. As soon as you need any data manipulation (i.e. arrays, computation, etc.) it becomes a pain and Python is the much better fit.
I've had Perl change its syntax on me and break my pet monitoring system too often to make me feel good about Perl. It hasn't been too hard to keep it running (20 years so far), but starting fresh I'd probably use Python.
Python is much cleaner code than Perl for the most part as well.
However, for anything that should run forever, make sure you have a copy of all of its source code AND its libraries AND the source code for it's compiler. Repo rot is a serious problem over time.
I see AWK as a general-purpose output filter and aggregator, something like a programmable grep. You read another program's output line by line, and output it filtered and/or summarised. Works nice when the format is known, but in case it isn't, error handling and recovery is not something I would enjoy doing in AWK.
Isn't awk that thing that has different versions with entirely different features and syntaxes? I think one of them ships with mac and the other with, uh, everything I've ever used anyway (maybe not *bsd or something). Or was that sed?
I only ever use it on my own systems so awk works fine for me and I use it regularly, but iirc it's not true that you don't have to worry about versions.
Python is where I don't worry about versions. Everyone's got python3 by now (word got round) and most basics, like print(), works just fine in 2.7 (the main py2 backwards compatibility thing I run into is bytes vs unicode strings; if the script needs to work with raw bytes, you'll just need any python3 version). The issue I run into is with Windows people not having python installed, and (worse) not being able to install it in 30 seconds with one command, but that would be the same with awk.
