I voted both John and Paul. For pure aesthics, I vote Paul. He has a very pure and angelic voice that can be very soulful if it wants to be (just listen to Let it Be). John, on the other hand, has a voice that fills your ears, pokes at your brain, runs down your spine and hits you in the heart.
Together, the voices had the perfect blend, the devil and the angel on your shoulders, making you confused on where you stand and totally take over your whole being.