But WIPO does not have the clause-driven business of the American Arbitration Association. And the AAA sometimes tries to flip cases from arbitration to mediation in circumstances that seem appropriate. So you can choose your mediator. Choose an individual mediator as you choose an individual advocate. As if the person is an excellent mediator, not whether he or she was a good judge or a good litigator.
Some mediators are more evaluative than others.
Be candid with yourself and the mediator about what sort of process you want. You are, after all, paying for it. Good mediators have a range of styles, just as good litigators do. Some styles are better for some disputes than others. Too much is made of expertise.