Performancetest: Flash/AS3 Processing/Java and openFrameworks/C++
I know in the AS3 world there is a popular performance monitor called stats, you can find it here. Honestly I think you may be comparing apples to oranges. My initial assumption would be that openFrameworks (C++) outperforms Processing (Java) and Processing outperforms AS3 for many of the problems you will be exploring. I am sure there are many Java performance monitors and C++ monitors that you can plug into your Processing and openFramework programs to collect the data you need or you can roll your own.
Of course you also need to identify what exactly you will be testing. My initial thought would be to test framerates, memory consumption, CPU utilization, and execution time. Personally I like to develop particle emitters and push my programs to the limit on the number of particles it can process. You will quickly see that Processing and openFramworks kicks AS3s butt with this.
Well I hope I helped.