I like Python mostly for the great portability and the ease of coding, but I was wondering, what are some of the advantages that C# has over Python?
The reason I ask is that one of my friends runs a private server for an online game (UO), and he offered to make me a dev if I wanted, but the software for the server is all written in C#. I'd love to do this, but I don't really have time to do multiple languages, and I was just after a few more reasons to justify taking C# over Python to myself.
I'm doing this all self-taught as a hobby, btw
Well, the ease of coding is debatable.  I find C# easier to code when you factor in the help you get from teh IDEs (e.g. the free Visual Web Developer).  
So, portability is less of an issue if you factor in Mono.  Performance can be better in some scenarios.  I find the online documentation to be generally better in .NET.
Have you considered IronPython?  If you guys are willing to use one of the .Net distros that have the DLR in them (4.0's your best bet there, but some of the DLR betas are alright), then you can write C# code and Python code and have them work together w/o any difficulties outside naming conventions being a bit different.
what are the advantages of C# over Python