Unfortunately the best training aircraft aren't available to the civilian market due to cost. I trained in the UH-1, an option that simply isn't even a choice to the civilians of the world. But, the Huey has huge rotor inertia, massive amounts of power reserve and is a turbine. The instructor can dictate the flight profile to simulate a power limited situation, but there is plenty of forgiveness that allows the instructor to have a very large comfort buffer. I'm not saying that something as large as a Huey is required, but a training aircraft should be easy to fly and very forgiving. Let the instructor dictate the level of difficulty, not reality. Do you really want to sit next to a ppl student while he attempts an approach with only hover power available?