After hearing some auditions recently, where I was not adjudicating, I had singer lamenting to me that they didn't get the opportunity to sing their favorite aria (since the judges didn't ask for that one).
My question to the singer was - why didn't you offer that one???
The simple point here is that always assume that "they" might not ask for your favorite tune. The way around this is to OFFER it.
I have said this before in different ways, but never, ever leave your best stuff on the table - assume you'll get one shot, and give them your personal desert island aria. Don't worry about what you think they might want to hear, or what they might be casting, etc.....
Your best chance to win a competition or to get hired is to sing what you do best!!