I think that playing the best Chopin is a matter of being in the right frame of mind, as well as doing the right technique. Context matters. I've read that some other respondents are tired of Etude Op. 25 no. 6 (the etude in thirds, eh?). I really go for it. The thirds can be made to have a wonderful, dreamy, capricious, glistening, magical effect. And what to play after finisihing it? The mazurka opus 50, no. 2, in A-flat major. It will sound as though it's coming in, majestically, on a red carpet. Another thing to do to prepare for the competition would be to read biographies of Chopin. To play the nocturne, opus 48, no. 1 with maximal effect, I can't think it would hurt to be familiar with the historical background of how Polish national aspirations were crushed in 19th century Europe. Opus 48 no. 1 has what amounts, in effect, to an anthem in it; that gets drowned out by the sound of gunfire. I wouldn't do Opus 25 no. 12 unless I could do a really, really, REALLY good job bringing out exactly the right amount of accenting to every semiquaver played at exactly the right time. And as for Opus 10, no.8 -- well, it's no Brandenburg concerto no. 5, or Appassionata Sonata. Leave it in the book, for posterity to ponder.