From what i have gotten from looking at the score and watching it performed/practiced, and talking with friends, it seems that the gaspard overall is more difficult to learn and get to where it should be rather than performance. It seems to flow very well once it is in the hands, but practicing and watching tapes and performances of Islamey its just so unstable ALWAYS....not to mention the stamina required....Also, the gaspard does indeed have a larger range of coloring, but as long as its all relative you're in good shape....Islamey is one of those pieces that is rarely EVER played like it was intended to be played, with the tenderness and romance of a romantic piece of music. The ONLY player i have heard play this like a real romantic piece is Gyorgy Cziffra...and Barere's recording isnt half bad...but 9 times out of 10 itss played wayyyy too fast and wayyy too loud..not to mention extremely dryly (sp?)
Cheers!
Ricky