I don't play the sonata, but if I ever take the plunge, I would choose the 1913 version. It's textures are far richer. It's too bad that Rachmaninoff got onto his simplification kick. For example, his similarly revised Melodie, Op. 3 is a mere shadow of the lush, ultra-romantic and filagreed original version that he himself played in recitals. Although the 1931 sonata and the later Melodie must be considered "official", I still prefer the originals!