That's the thing. If you're adamant on a dynamic language you won't even be looking at C# or Java. It has nothing to do with the quality of the language, but the choice of programming paradigm.
Both C# and Java are quality languages. Given the choice between the two, I choose C# anyday. Sadly, this means Visual Studio... Resharper makes this slightly more tolerable.
To be honest, I think I'm just using it for the wrong thing - I don't tend to work on big, collaborative projects which is where Java really shines. Meanwhile, C# has a few conveniences (such as LINQ and rectangular arrays, off the top of my head) which seem to me to make scripting and small projects easier.
What aspects of C# makes working on large collaborative projects difficult? Not sure where you are going with this.
Unless you meant Team Foundation Server / Visual Source Safe pukes.
None. I was just talking about my issues with using Java for small projects, not using C# for large projects. My argument is that C# covers scripting and small utility programs adequately, while Java seems to require more boilerplate.
C# would be my natural choice for projects large or small.