This is the never ending arguement for which there is no right answer so base your decision on some logic. First, as someone else stated, slick shows are typically regulated to the south where a different type of cattle are raised. Second, what type of shows is the state fair and other shows in the area? Thirdly, you cannot level the playing field. Accept it. Fourth, if all you want to teach is husbandry or nutrition, you can learn that in a classroom. Don't need an animal for it. Finally, everyone seems to agree that those who do well in either show will continue to do well if you change it up. So it doesn't really matter. Just because you have a hair show doesn't mean you have to grow hair.
Really it comes down to finding good judges that do look at the calves as a whole and not just the "pretty calf". Leveling the playing field is a pipe dream. I have a son who shows and over the years we have laughed about how the pretty teen girls always seem to have an advantage in the showring. But then, that's life.