Bokeh Battle 85mm Zeiss Otus vs Sony G Master
The video above from DigitalRev TV shows the advantage of electronic viewfinders found on Sony cameras. The evf betters optical viewfinders by providing a more accurate way to manual focus lenses. The Sony A7r II provides a magnified view for focusing. It also has focus peaking which highlights portions of the image that are in the focus zone. So getting the shot with the Otus is a much easier task with an EVF.
Another advantage shown is that Zeiss only provides autofocus lenses for Sony - the Batis line. The A7r II had no problems locking focus with the 85mm G Master. Canon and Nikon shooters can only use the Otus and Milvus line, which Sony shooters have access to as well.