If you talk of performance I can assure you C++ beats Java..
We're in GSM network element development so performance is of utmost importance, we've tried both (C++/Java) and concluded that Java is for O&M (Operation & Maintenance GUI...) and C++/C is for CP (Call Processing)..
There are some small part of Java code that JVM manages to execute fast enough but when thousands of lines of code written by lotsa guys is put together it's invariably slow.