Benchmarks generally show C# outperforming Java, but not to a degree that most people would worry about. Performance-sensitive applications are still going to go for something native.

One of C#'s biggest assets is Anders Hejlsberg of Turbo Pascal fame. He's been in charge of C# since its inception. He's done a very good job of keeping the language clean and concise, and generally ahead of Java when it comes to adopting features like generics and functional programming.