A correct approach to benchmarking blueprints vs C++ would be to make the engine’s impact on timings negligeable, by doing very intensive computation that last for multiple seconds per frame.
For example a code to do an n-body simulation like http://benchmarksgame.alioth.debian.org/u64q/program.php?test=nbody&lang=gpp&id=1
The benchmark posted here only shows that C++ is indeed faster than blueprints but nothing more.