My order of favorites at the moment is 4-2-3-1. The only one I've played is No. 2, and I think I'll play it again in a couple years. Here's what I think about it:
-You have to know a LOT about good phrasing and structure to make the slow section work, as well as the technique and touch to voice it evenly and sound horizontal - like a long, flowing line - instead of note by note or beat by beat.
-Those dotted rhythms have to be perfect. Don't cheat the short note and make it too quick, causing it to be snappy, and don't cheat the dotted note before it, which would probably cause you to rush or make the short note too long.
-Oh, and I feel like phrasing in the slow sections is not simply "louder/more as the pitches in the melody get higher, and softer/less as they get lower" because it doesn't fit the bigger idea that way.
And with the fast sections, I think it takes someone with a technique strong enough to stay relaxed during the descending arpeggio figures and ascending tremolo figures. Also, you've got to be able to play series of octaves in your left hand, without tensing up or without looking. Basically, you can't focus on each individual note in your LH; it has to be able to go without worrying where the notes are. You've got to worry much more about making a good musical line out of it, instead of just banging out each octave.
And with the coda, you've gotta be able to rapidly repeating chords without tensing up (I like using my wrist as the "hinge" for those motions). It gets even trickier when the RH has the chromatic motion in the bottom voice, and the repeated note in the top voice with the pink.
Those final chord-arpeggios are difficult to do and keep the thumb relaxed-if you tense your thumb up, you tense up everything. And, once again, the LH octaves.
Topic: Chopin Ballade no 2