I don't know the last one, but out of the first three, the Pathetique sonata is definitely the most impressive, but I assume you're talking about only the 2nd movement? It's a very nice movement, and not exactly easy, either. Well, I think it's easy but I remember learning it when I was younger and having trouble with it. I'm working on the first movement now. I think the Schubert impromptus are more difficult than the 2nd movement of the Pathetique, though....but I've never played those two, so I'm not really sure (I've only played the A-flat minor one, and that one is more difficult than the 2nd movement of the Pathetique), but I think the 2nd movement of the Pathetique would be more effective, if you play it well.

In my piano pedagogy class this semester, my teacher gave a lecture one day on Beauty Pageant Pieces. She's had several after hours pre-college students over the years that have wanted to learn something impressive for a pageant talent thingy, compressed to 90 seconds. I imagine that's what you're after. Things that aren't too difficult but sound difficult...the Khachaturian toccata is one of the pieces she mentioned...

Good luck! It seems a bit odd to play a piano piece to audition for drum major (usually you have to conduct and do some mace work), but if that's what they want, I'm sure you'll do fine!