DASH vs MS PowerShell

Dash has a very fast startup, this happens because the shell is started a lot of times during boot and dash minimizes the work it does during this process.

It is designed to be very lightweight and has no support for shell specific extensions that are not POSIX.

DASH is the default shell for Debian based systems due to it speed, full POSIX compliance and low overhead.

It's fully POSIX compatible, so if your script runs on dash it will probably run on all other shells.

It's a clone of the original System V4 Bourne shell.

The help system is designed to evolve over time; running update-help downloads the latest content.
When searching for help on items, you can simply type help commandname to get information about a command.
If you're not sure what you're looking for, but have a rough idea, you can search on partial command names, or even specify specific verbs to get a list of commands potentially of interest; e.g. help -verb write.
The information in help gives a good overview of the commands you're looking at, along with code examples, so you can see real-world usage without resorting to the web.

When calling a method with multiple parameters, rather than passing one variable per parameter you're able to "splat" one variable to the method, with the parameters taking their values from its properties.

Commands can be chained via the pipeline, allowing output from one to be cleanly fed as input to the next.

PowerShell is installable through Chocolatey.

The language can wrap and interact with code written in other language's, making it highly extensible.

Though Windows Powershell only works on Windows, the open source implementation Pash (http://pash.sourceforge.net/) allows the same language to be run on other OSes.