recommended target languages (performance, features, maturity) 
If you are not bound to a specific target language, how to choose the best for your problem?

In my case, I need to decode large proprietary format binary files into some more standardized structured format such as e.g. JSON.

For this I care about performance and reflection support (such that my decoder program can dump all attributed to JSON without access them by name in source code).  

1. Performance:
    * For my Problem C++ was 10x faster than Python
    * _Any experience with other languages? I would expect that Java and C# almost match the C++ performance_
 
2. Reflection support:
    * Not in C++ but most other languages such as Java, C#, Ruby, Python
    * _Do I need to use language reflection to keep the decoder program code independent of the ksy file, or is there other support to traverse the parsed object tree with all attributes?_   

3. Maturity and Ease of Use: 
    * I had no problem with generated python code.
    * Some minor problem with generated C++ and Java Code
    * _Any experience with C# and Java? Which are more robust and or easier to use?_

