JD,
Looks can be deceiving...Just because there appears to be more roiling action on the surface with one diffuser over the other, it does not mean that it is necessarily moving more water. If there appears to be water being lifted in a "dome" above the surface of the water, this would indicate course bubbles. All airstones that I know of are course bubble. Most "tube style" as you describe them are fine bubble. While the surface aesthetic of a course bubble diffuser may appear to be moving more water, they actually move less water than a fine bubble diffuser. When we see this "doming" affect with our fine bubble diffusers, we know that there has been damage to either the diffuser itself or the fitting that receives the feeder tubing.
