Simple truth: the OVF is a passive device that has tied camera progress for years. This has been supported by Canikon being the benchmark of photography and by their being uninterested in developing EVFs.
That said, the EVF is a dynamic, active device that gives plenty of advantages. Magnification, exposure preview, peaking, zebras, etc are only some of them. More than that, an EVF can be extensively developed and improved over time, OVFs not quite. OVFs are the past, EVFs are the future, and we are now in a transition zone.
If any of the nay-sayers in this thread had actually tried the EVF in the a7 or OMD, probably they would have a different opinion.