Scriabin has some gorgeous etudes (opus 8 no 5, 12) (opus 2 no 1), Liszt's are in general harder than chopins. PE 3 (la campanella), PE 6, and TEs, 4,5,8,10,12 are harder than all of chopins.
They are all good pieces, but some of Liszt's can be a bit show offy with not enough emotional depth. Chopins hardest are opus 25 6, and 25 11. Sorry to bring up difficulty, but if you are only trying to impress the judges, it will help as long as you can play them properly. Alkan's also got some, but to me, they are just completely show off material, although I like festin d'aesop alot. Rachmaninoff has some as well. TONS of composers had etudes.