As you say, what you choose is purely a matter of personal preference.
For me, I like C# better because of it's huge user base, prevalence of publicly available solutions and help, and is closely related to other dominant programming languages like Java and C++, making skills more transferable and solutions more adaptable.
I know enough PowerShell to be dangerous and if dialect between C# & PowerShell are similar, then it's easier for me sharpen (pun intended) both skills at the same time, during my learning process.
...but that's just me.
HTH,
Phil Streiff, MCDBA, MCITP, MCSA