Again, why compare one piece with another? It is absurd and illogical to do this. Both of them are written in different styles, in different times, and by different composers. Each composer has his own language. Chopin has his, Liszt has his.
Neither of these pieces are too difficult, and are very accessible. The Chopin Fantasie-Impromptu should not be a problem as long as you mastered your 3 against 4 polyrhythms. Remember, polyrhythms are much easier to play in fast than slow, and they sound much more even fast than slow.
With Liszt, everything fits the hand, and those who know their basic technical idioms; scales, arpeggios, chords, octaves, broken chords, broken octaves, thirds, 6ths, etc. should have no prolem at all. There are no awkward moments in Liszt, and contrary to common belief, his music is very accessible and easily understood by advanced pianists.