That's a good question! I suspect (though I have no evidence of this) that the opening show helps prepare the jury for their task. In the past, when the opening show was a competing show, it seemed it was virtually impossible, statistically speaking, to win Gold. I know that Fred did the analysis once. As much as the jury are trained by watching videos, seeing a display from the seats at La Ronde is a very different experience and, if you have no reference, it's hard to judge the first show fairly (more likely to be under-marked, I'd think, in case subsequent displays are better). There's certainly more winners from the 2nd half of the competition than the first.
Personally, I'd like to see at least 7 competitors - then the odds of winning any particular prize are lower than 50/50. I liked the years we had 9 competing shows and then a closing
Paul.