The way I see it is this :
Lets work with a 35L tank say, nothing to big. If you put around 1-3 bps of Co2 in to that tank, that would normally be the right amount - thats what you would be aiming for right!
So you compare pumping 3 bps through a Rhinox5000 ( approx 4cm diameter ) as a pose to a nano diffuser by Dazs ( approx 1 cm in diameter ) To my experience you would find a healthy fine mist of bubble lifting off the nano diffuser at that bubble rate, yet with a Rhinox you would find a small section producing bubbles, and IMO much larger than with the nano. The larger bubbles have less surface area and rise to the surface much quicker.
Also, think about it like this.
To much pressure on a nano diffuser. eg 5-6 bps could force the Co2 line to constantly pop off. On the other hand, to little passing though a large diffuser eg 1 bps would result in a week delivery of Co2 and it would no doubt find the weakest point of the ceramic plate and do as described above....( finding the path of least resistance ) = large bubbles rising to the surface to quick. The right size diffuser gets away from this problem as all of the diffuser is used, thus more efficient.
You do also need to take into consideration the quality of the ceramic plate. Even if you get the right size given its pressure requirements, there still could be flaws which would result in rapid bubble loss rising to the surface,
That my slant on it any way, and it works for me.