I would think a degree based on an exam, assuming it was appropriately difficult, would be better than a diploma at determining a students proficiency.
I have two masters degrees but also think a Masters or Doctorate based on appropriate exams would be better than the current degreees. Yes I know all about the orals, theses, dissertations etc.
I would far prefer a teacher who passed a difficult exam to get their certificate to one who completed an education degree program at a University.
The universities are filled with immigrant professors with accents so thick that you can barely make out one sentence. They couldn't teach well enough to save their daughter's life, but they're really good at passing exams.