The idea of ranking Chopin etudes according to difficulty is an interesting problem. In general, people with long, thin fingers have an advantage over those with short, thick ones. Some etudes are not so hard to get the notes right on, but hard to get the right rhythm or dynamic shading. Based on my experiences of 45 years of trying to play them, I would rank the ones in opus 10 as follows, from easiest to hardest: no. 6, no. 9, no. 11, no. 7, no. 3, no. 12, no. 10, no. 5, no. 4, no. 2, and no. 1. I left out no. 8 because I've never tried it, and with all due respect to Chopin, it's no Les Adieux sonata. In opus 25, from easiest to hardest: no. 7, no. 1, no. 10, no. 2, no. 12, no. 5, no. 6, no. 11, no. 8, no. 16. Nos. 3 and 9 haven't been tried yet.