Yeah depending on the scene you can get different performances, I did a few tests if that might shed some light :
TLDR : It’s more efficient in lighter scenes and heavier scenes performs better in OGL…
OpenGl isn’t developed anymore, Vulkan is the future and will allow interesting stuff, however as Ace said it’s the initial implementation, the first step is making it stable and eventually optimization will come.
Making it default is also a way to make sure it’s widely tested, they might not remove OGL yet…
Probably the hype comes from the fact that it’s a lot of work to get it done and it will allows a lot of stuff. Then nowadays everything on internet is explained like if everything is going to change for the best without necessarily understand all the details !