I have Cortot's Op. 25 etudes, and I've learned quite a bit from them. The other day I was in the music library (IU) and found a Cortot edition of Liszt sonata and an urtext. I went for the urtext. (First of all, the Cortot wasn't translated in this case). I think that one can learn his method from the Chopin etudes alone, and it is then valuable to transfer them by oneself to other pieces, i.e. Liszt Sonata or Chopin Scherzi.
Food for thought.
Michael