I have played
Op 10 no 1,
half of op 10 no 2,
op 10 no 12,
op 25 no 1,
op 25 no 2,
i'm working on op 25 no 6,
op 25 no 11,
and op 25 no 12
Out of these, I found op 10 no 2, op 10 no 13 were the easiest.
The medium level would be op 10 no 1 and op 10 no 14
The most difficult level would be op 25 no 11, op 25 no 12, and op 25 no 6
I do believe that the hardest is the winterwind (it is easy to lose if you don't keep it up) but the one that gave me the most trouble is the Ocean Etude.... to get it a tempo is quite difficult but once you have it, you can always relearn it pretty quickly.
Op 25 no 6 is giving me some trouble... i've been playing it for almost 3 weeks now and still can't get it a tempo. I hate it when the nasty cross overs come in the right hand on the beginning of the 2nd page. To get those unaccented/fluent is difficult.