Musically the 3rd ballade is very difficult(so is op 48 no 1), technically, some parts reminds of the Nocturne's doppio movimento, but the parts in the ballade are more difficult. Also, it's longer, and has some fast passages and double notes that require a technique you don't really need for the Nocturne.. Also, I don't think I have ever heard anyone play the doppio movimento part at 120 quarter notes per minute... More suitable would be something between 80 - 100 quarter notes per minute, which still makes it fast and very hard. I play the Nocturne, it's insanely difficult, have you played the ballade? Also, about op 25 no 10, ones again I don't really agree, as the octaves in op 25 no 10 goes on for much longer.