Piano Forum

A big benefit is to think about the interpretational directions given in the Grandes Etudes- you might well use them in the 1851. 

Personally, I find that the introduction in the Orchestral Version of the Mazeppa to be superior to the original.  When I learn #4 of the Transcendental Etudes, I plan to use a mixture of that introduction with the original.  I would present hte original chords, and, in place of the cadenza, I would play part of the Orchestral introduction.  The first 11 bars would be in parallel octaves with the left hand playing the countermelody.  Then I would play the right hand in detached octaves and counterpart in left hand legato octaves.  I would clothe in pianistic garb the next 15 or so measures.  At the FF, I would use a device Liszt himself used when he played Schubert's Wanderer Fantasy in staggered hands, then I would play some "blind" or "Liszt octaves" at the place which LIszt's orchestral score is unison, and then play diminished seventh arpeggios in both hands from the middle of the keyboard up to the top and take down from the top of the keyboard the last portion of the Etude's Cadenza and begin the first theme.  This obscures the tonic for longer, builds greater tension, and, I feel, makes for a better effect.

I would also put in (From the 1838 version) a hint of the melody of the place in the etude between strophe 4 and the second time the octave cadenza is presented - it is a very beautiful effect, hidden in mere rhythm in the 1851 version.  You should listen to it for that understanding alone.

What I'm trying to say is that I feel that you have the right to mix and match different parts of different versions of a piece, especially when it comes to Liszt.  Thus, looking at the 1838 versions, you might find some passages you like better.  I know of more than one person who would put in the presto feroce coda back into the 1851 version of the Etude in F Minor.