Very interesting analysis. Still, when comparing to C++, we have to consider that with a game that actually does something (game logic, interaction etc.) C++ advantage would be much bigger.
Actually C++ advantage would be smaller, since the test isn't at all GPU bound. It's basically testing how fast you can copy data through the JS <-> C++ FFI into the GL library.
A test that stayed within JS would optimize better and perform better relative to C++.
