Although I'd never limit myself to one set of compositions, the Mazurkas or the Polonaises would be my choice. I feel they are most capable conveying Chopin's vision. They are decidedly Polish and were close to Chopin's heart.
The etudes would be my last choice. Brilliant as they are, each is relatively singular, with the purpose of creating art through a technical pattern taken to the extreme.
I could also find reason to choose the nocturnes, waltzes, or preludes. Each piece makes a unique impression on both player and audience alike.
A pianist should know all of Chopin...
and Beethoven, Bach, Mozart and.... you get the point.
Per Sapientiam Felicitas!