It's a short accented chord and the the two arpeggio lines are separated so it would be logical to play both hands simultaneously. If the composer had intended the hands to be played one after the other he could have written just a single arpeggio-line.
On Horowitz's own recording of the piece he appears to play the hands separately:

It probably doesn't matter either way: do what you feel sounds good.

It's a short accented chord and the the two arpeggio lines are separated so it would be logical to play both hands simultaneously. If the composer had intended the hands to be played one after the other he could have written just a single arpeggio-line.
On Horowitz's recording of the piece he appears to play the hands separately:

It probably doesn't matter either way: do what you feel sounds good.

It's a short accented chord and the the two arpeggio lines are separated so it would be logical to play both hands simultaneously. If the composer had intended the hands to be played one after the other he could have written just a single arpeggio-line.

 

It's a short accented chord and the the two arpeggio lines are separated so it would be logical to play both hands simultaneously. If the composer had intended the hands to be played one after the other he could have written just a single arpeggio-line.
On Horowitz's own recording of the piece he appears to play the hands separately:

It probably doesn't matter either way: do what you feel sounds good.