Tested C2 runtime against Construct classic and classic was 3 times faster. So if C3 is 3 times faster than C2, it only means it's neck to neck with the archaic Classic from over a decade ago.
C2 is fast enough for simple games though and C3 is more capable. Thing is they're not necessarily suitable for professional game development regardless of how fast the runtime is since the performance is bound by whatever wrapper is used and comes with baggage from the browser, like Chrome still having VSYNC issues as well as trouble streaming with software like OBS.
This is why all the performance tests on the blog are on 30fps instead of a vsynced 60fps. A construct game simply will not hold vsync under slight load. Also you cannot run a game at 30fps unless you increase CPU load to slow it down.
It seems Chowdren is presenting a native solution that has already demonstrated superior speed on top of fixing vsync, input lag and game streaming issues, so looking forward to where it goes.
As things are now, I would only recommend using C2/C3 for making browser games.