Significance of hand placement in forming mudra

In Suzuki's "Zen Mind, Beginner's Mind" (online copy here ), instruction is given on how to form the specific hand position (mudra) when meditating. He advocates "put[ting] your left hand on top of your right." This is the position I have been using in my short months of meditating, and is the position also taught to me at my local Zen center. However, this resource , by Ven. Mahathera Nauyane Ariyadhamma, advocates the opposite: "back of the right hand over the palm of the left." Question: why the difference? and, Does it even matter?