Area/State are against someone else therefore, region provides the snapshot of where you are against the rubric meanwhile Area/State or based on the preferences of the judges compared to the other ensembles.
I don't like the new trend therefore, as a judge I will naturally be prejudiced towards the more traditional shows versus the new shows with hits every 20 seconds, no melodic lines, or run to a blob, yell through your instrument and then run to your next blob/hit point. See how that works. But if I have to judge against a rubric which is feet in time, uniform styles, sound quality, intonation, etc. I take the bias out and now we can actually see if we are a 1, 2, 3, etc. level band.
At state everyone can march. The question is who paid the most. Region, money doesn't matter as long as you look the same and sound like a band.