I don't have any benchmarks handy for you, but this post is very interesting, you might have seen it:viewtopic.php?f=24&t=2230
Migi32 did some analysis on the final results, he/she graphed the results by country and also by programming language. The x axis shows the expected result, y axis the actual result for each participant in each group. Expected result is a player's rank in their group divided by the number of participants in that group, multiplied by the overall number of participants. So if the participants in your group tended to have greater expected ranks than the actual ranking, your group performed well.
It's up to you to determine why certain groups did better than others. Some one has suggested, for instance, that the language barrier might have caused fewer 'non serious' entries from Russia than from English speaking countries. Someone has also suggested that it was more difficult to enter a C++11 submission than a C++ submission, which might have accounted for the C++11 group performing better than C++ in this graph.
I think also that if you understand the difference between C++11 and C++ (which I do not), you are probably a more experienced programmer. I think this might also explain the difference between VB and C#, because I'm pretty sure they are basically the same language with a different syntax.
Some languages are definitely faster than others, I would think compiled languages are faster than interpreted languages. I think C should be the fastest, but it might be difficult for a lot of people to keep code organized without OOP.
As for myself, I think I'm going to do C++ next time (I wrote ants in C#), but you could probably do well with any language if you're smart about it.
I read your other post, you have good ideas, I'm looking forward to seeing more posts from you.