How much less libraries are there for Mono than for Java?

I lack the overview over both alternatives but I have pretty much freedom of choice for my next project. I'm looking for hard technical facts in the areas of

* performance (for example, I'm told Java is good for threading, and I hear the runtime code optimization has become very good recently for .NET)
* *real world* portability (it's both meant to be portable, what's Catch-22 for each?)
* tool availability ([CI](http://en.wikipedia.org/wiki/Continuous_integration), build automation, debugging, IDE)

I am especially looking for what you actually experienced in your own work rather than the things I could google. My application would be a back-end service processing large amounts of data from time series.

My main target platform would be Linux.

**Edit:**
*To phrase my question more adequately, I am interested in the whole package (3rd party libraries etc.), not just the language. For libraries, that probably boils down to the question "how much less libraries are there for Mono than for Java"?*

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FYI, I have since chosen Java for this project, because it seemed just more battle-worn on the portability side and it's been around for a while on older systems, too. I'm a tiny little bit sad about it, because I'm very curious about C# and I'd love to have done some large project in it, but maybe next time. Thanks for all the advice.