Unlike others, I think the 3rd scherzo is MUCH more difficult than the second. It's almost as difficult as the fourth scherzo, one of Chopin's hardest pieces. The first section forces you to go rage octave and play them really fast. The D-Flat/E Major sections has notes that are two times faster than the first. I think you should tackle the first scherzo, my favorite of the bunch. It's difficult, but half of the time, you're repeating passages that you've played, like, twice. The second scherzo is a good one to start, but you should master the first then go to this one.
And btw, the 4th scherzo is almost as hard as the 4th ballade, so you probably have to be Rubenstein level to play it.