Marcus Nasarek from Linux Magazine did a comparison of Bash vs PowerShell, you can check it out in this PDF file.
Whereas Bash typically relies on a
combination of newer tools and classic
Unix utilities, the PowerShell has its own
set of command-line programs. Win-
dows refers to PowerShell commands as
cmdlets. The PowerShell cmdlet called
Get-Process is a counterpart to ps, and
the cmdlet Get-Content corresponds to
less. PowerShell differs significantly from
previous Windows command shells. In
this article, I look at how Windows Vista
PowerShell compares with Bash.