This thread starts off with a false premise:
I think that you can take a dressage rider and put them in the hunter ring and they will kick butt, but if you take a hunter rider and put them in the dressage ring then they won't do so well
and then veers accidently onto a correct premise worthy of discussion re: classical vs. modern dressge.
Let's get rid of the false premise, that hunters and dressage are judged on the same objective standard and hunters somehow fail to measure up, once and for all. A dressage rider in the hunter ring will not kick butt, and a hunter rider in the dressage ring will fight against their forward seat training and struggle to adapt. A dressage rider, in a full seat, riding a dressage quality gait, is going to look pretty silly in the hunter ring and is going to do the opposite of well. The goals of the two disciplines are *different*; it's comparing apples and oranges. A hunter is supposed to move freely forward on light, passive contact and maintian pace and balance with little or no interference from the rider. Done correctly, it's lovely and a joy to watch and completely antithetical to the principles of dressage, which expects that the rider be influencing every step and produce a horse that is completely submissive and obedient to the rider's aids.
Because of that difference is goal and training philosophy, I will say that it is easier to master the basics of hunter seat riding than it is to master basic dressage. AND when learning dressage, as I did, from a hunter seat background, you struggle to stay in a deep seat and to ride every moment of every stride. However, that struggle is no way more or less humiliatating than a classically trained dressage rider getting on a well schooled hunter and confusing it to distraction with a pushing seat and over active aids. If that well-schooled hunter is a TB, particularly one that's had race training, the dressage rider's ride is going to be....short.
Both disciplines are based on sound principles of horsemanship and have value in and of themselves. It's even possible to ride both disciplines and love them both. My hunter seat training informed my dressage riding and my dressage riding informed my hunter seat riding. That's the whole reason to study another discipline. A side benefit of studying another discipline is that you gain enough perspective and understanding of the new discipline and can avoide false comparisions and mindless bashing in the future.