Is sodium hypoclorite better than calcuim hypoclorite for keeping the dust from settling at the bottom of the pool?

If you are referring to dust from wind blown dirt etc, neither type of chlorine has any effect on the amount of dust settling on the bottom of the pool. If you are referring to white chalky dust, that comes from calcium hypochlorite. Cal Hypo is 65% chlorine and the other stuff generally does not dissolve. You should dissolve the Cal hypo in a bucket of water and poor the liquid into the pool and toss the remaining white stuff.