The Scriabin will give you good experience with very wide LH arpeggios and chordal passages. This can definately cary on to many other pieces, plus its really fun to play! Things to focus on: pedal point, harmonic prgression, balance in the different levels of activity. Focus on creating contrast and color each time a motif reapears. There is a chain of 4th species counterpoint used very effectively near the end.
The prelude sounds awesome, just heard a random recording of it... It sounds so frustrating lol...