Bash ports on Windows can be messy especially if it involves non-Latin codepages, especially when it involves language like Japanese, which frontend is still not migrated fully into UTF-8. (Also WSL handles it more gracefully.)
I am program in C# a lot, so extensibility via CmdLet is also interesting. (Although, I haven't explored this much, yet...)
I can't comment on the other options you listed, but I would agree that PowerShell has good features for parsing arguments (if you use advanced cmdlets, which only require one extra line to enable on basic cmdlet code, for [CmdletBinding()] ). Aside from built-in attributes for enabling common argument checks (like checking for nulls), you can completely customise parameter validation using ValidateScript, which allows you to set up a script that must evaluate as true in order for an argument to be valid. I'd be interested to find out if any Unix command line scripting language offers something similar.