I live 5 minutes from the site of about 7 top hunters shows a year and numerous schooling shows. I actually get to watch quite a few hunter rounds every year. (God knows I have to do something if I'm there for a class and we are waiting interminably for someone to show from another ring.) Here's what I know: what passes for a lead change in the hunter ring on average, in general, sucks--oh, it's acceptable for a hunter ring, but if you are judging in terms of a correctly given (much less ON command since you seem to be about "control") classically and correctly performed flying lead change, not so much.
Going back to watching the Emerging Athletes clinic--an invitation only to the best and brightest young jumper riders with the likes of Linda Allen and Melanie Smith coaching-sure they got their changes (and obsessed about getting them) then almost every single one of them while on the correct lead would take a corner with the shoulder popped out. It happened so many times it got to be funny. They were simply fantastic riders 3 strides before, over, and 3 strides after, but on the flat, between fences? 75% of them didn't demonstrate the skills or understanding to ride out of a paper bag.