trolling is an art ;).
but seriously, VCM is slightly slower, because it is harder to parallelize right. But since VCM is in a way a combination of ALL other algorithms used for unbiased rendering (except for metropolis ones), it is very easy to modify it to get these algorithms (bidir, progressive photon mapping, path tracing, light tracing). And since bidir is very complicated and demanding, it does not make sense to maintain a separate implementation. I'll just have to make the multithreading more efficient.