What is the advantage of an optical viewfinder over an electronic viewfinder?

None of the above.

The advantage is that the camera almost disappears, and you are looking directly at the subject. You see directly what you want to capture, and it makes a difference, which is almost unexplainable.

It's a Zen thing. It either matters to you to see things that way, or it doesn't.

Leica had it the best. The next best thing is an OVF on a DSLR. Almost as good, but a small step down.

That sounds obscure, but I can'd do better.