In terms of the education/certification between the two, there may not be any real difference. It would be assumed, however, that the Master Trainer would possess a gold instructor level before becoming a Master Trainer.
Master Trainers are considered “trainers of trainers.” In other words, they carry the responsibility of representing the organization and the weight of certifying other trainers through the levels as laid out by the organization. You normally can’t just apply to be a Master Trainer (which is the norm of any organization that endows the title of “Master Trainer”). You normally have to show a level of dedication and passion for teaching others how to teach.
There’s usually an expectation that the Master Trainer’s techniques are flawless, and that they can train other trainers to properly troubleshoot and instruct their clients.