I often get this question. I’m not sure, the right hand, the bow hand is hard because it is mostly responsible for the tone, and tone production requires so much awareness of the muscles and how they can be manipulated to create sound with incredible flexibility, precision, speed and accuracy. The left hand has also to be relaxed and learn incredible feats with finger speed and accuracy with fluid motion. Both hands are harder. Really the requirement is the hands be fairly equal but operate independently and cooperatively. When would a person learn on a violin configured to go on the right shoulder? Hmm. I’d have to say if there were digits missing on the left hand.