Python works as a great, all-purpose tool if you’re looking to replace CMD and BAT scripts on your Windows boxes, and can also be written to run scripts on your (L)inux boxes, too. It’s a great, flexible language and can handle many tasks you throw at it.
That being said, PowerShell is an amazingly versatile tool for administering all manner of Windows boxes; it has all the power of .NET, with many more interfaces into MS products such as Exchange and Active Directory, which are a timesaver. Depending on your situation, you may get more use of of PS than other scripting languages just because of the interfaces available to MS products, and I know MS seems to have made a commitment to providing those APIs in a lot of products. PowerShell comes installed on all current versions of Windows (Windows 7+, Windows Server 2008+), and is fairly easily installed on older versions.
To address your edit that your scripts will be used to launch other processes, I think in that case either of the tools fit the bill. I would recommend PS if you plan on adding any admin-ish tasks to the scripts rather than just service calls, but if you stick to what you described, Python is good.