I just remembered another trick you can use when someone is arguing one tack; get them to commit to the ultimate deliverable. i.e. "So you say we should do XYZ

I just remembered another trick you can use when someone is arguing one tack; get them to commit to the ultimate deliverable. i.e. "So you say we should do XYZ using PDQ, so will you be able to demo it for the customer next Tuesday?" Now to be right they have to get it done on time, and if they waffle you can assert your decision.