Until this moment, I believe I did more jobs in C# rather than Java (included professional job and other hobby kind things), but I am still a hardcore Java man. Using C#, because Windows is a key OS in the area of general public. This is very hard to persuade my friends installing JRE. In contrast, this is easier to say, "Yeah, let's install .Net, that looks like a plug-in for your OS." That is the major reason I did a lot of things in C#.
For Java, I think more comfortable with Java and my programs can be use my Linux and Windows boxes. Moreover, that is more opensource framework in Java than C#.
P.S. I love Joomla 1.5 so much, that is coding style looks like Java too.