My believe is that the only difference between dispersed bubbles vs bubbles in a riser is that the energy to lift the water is concentrated to a small volume using a riser, whereas dispersed still moves the water around but doesn't focus that movement to a small volume and hence doesn't seem to do as much and what it does do cannot be focused to doing some kind of work, like pulling water through a filter. In both cases the same amount of energy from the air pump is being added to the tank providing the pump is working equally hard in both cases.
In regards to noise I wouldn't know the difference between the big bubbles or small, I do know from snorkeling in rivers that areas with bubbles are quite noisy but, in these zones the fish do not seem affected.