What makes conservatory audition pieces good pieces?

Hello. I have noticed when I look up conservatory auditioin recommendations that some poeple said things like "Well, I think your Clical piece is fine, but your Romantic piece is not good for an audition". This has been said a few times. One time about La Campanella, which I can understand because it is overplayed and very hard to nail. But some other pieces that have escaped my mind have been called "not good", and I don't know why. Any idea why? I know that maybe they are overplayed and with a Prelude and Fugue you have to choose wisely because it is one of the most important aspects of an audition, but why others? I am speaking in the general sense as a part of an observation. Thank you.