Aside from the fact that Bash and PowerShell are both scripting languages, they are like lions and tigers. They were created for different environments. You can find bash on most every *nix installation, while you can find PowerShell on modern Windows. Behind those shells are two different operating systems, or ecosystems, if you will. Each shell is designed for the needs of its own operating system.
Each shell also has its inherent way of doing things. If you don't know bash very well, you will do things awkardly (no pun intended), but you will eventually learn simpler and more compact ways of doing those same tasks. The same is true of PowerShell. Practice leads to better code.
From my experience, PowerShell does some lovely things. I chose PowerShell because I managed many Windows machines, some of which I do not control. PowerShell was my least-common-denominator. (Yes, I know that makes me not-real, and so be it.) For me, PowerShell was the most appropriate tool for the job. If I had the same number of Linux boxes, I would have gone with Bash or Perl. Even if PowerShell were a measurably worse language by an order of magnitude, I would still have chosen it over Bash. And I'm not bashing bash (that pun was intended).