I am going to write a desktop application, but I am conflicted concerning which language to use. It (the desktop application) will need to have a good GUI, and to be extendable (hopefully good with modules of some sort). It must be completely cross-platform, including executable in various tablet environments. I put this as a requirement while realizing that some modification will no doubt be necessary. The language should also have some form of networking tools available.

I have read http://introcs.cs.princeton.edu/java/faq/c2java.html and understand the differences between Java and C very well. I am looking not necessarily at C, but more at a C variant.

If it is a complete toss-up, I will use Java as I know Java much better. However, I do not want to use a language that will be inferior for the task I wish to accomplish. Thank you for all suggestions and explanations.

NOTE: If this is not the correct stack for this question, I apologize. It seemed appropriate according to the rules.