Not all drivers are (created) equal…:). Have a top level (fast and consistent) driver drive these various engines and he will show/tell you they are quite different and one is undoubtedly better and faster than the other.
Especially in Road Racing I’m kind of amazed at all the different engines that can compete. 2014 models all they way to 2000 ICC’s to built Hondas. You name it, if you can drive it can compete.