Well, this is a very interesting question that I had never thought about. I play the bass Ab and dotted quarter note with the left hand, and the inner chord and the eighth with the right hand. I believe this is not only part of technique, but also common in Rachmaninoff's music the emphasizing of graceful movements of the hands, here caused by the quick motion of the two hands and then the passage of right hand over the left while it pulls back from the Bb quarter note. I also believe this movement gives more confidence and better accuracy, and the emphasizing of the upper notes. This is certainly a brilliant piece. If I were you, I would choose the one you feel fits the best for you, freely, since there are no footnotes on the score about it (at least on my edition). I hope this was helpful, and also hope you find the best solution.
Mario Barbosa