You should use the language you know best, which in your case sounds like C#. Plus, you already know some of an API that works with C#. That's a great recipe that you won't have with any other language or API right now.
The quality of games you make has everything to do with your skill as a coder and a game designer, and virtually nothing to do with the language you choose. The other factors you're hinting at are irrelevant at this point in your skill development.