I have the aquatech 3-in-1 diffuser:
And the fluval diffuser plus bubble counter.
Of the 2, I like the fluval system better for my paintball CO2 set up. It's more accurate for controlling the bubble rate (bubble counter) and the bubbles diffuse more evenly in the long
run. At first, I liked the aquatech version but as soon as the porcelain gets dirty, it distributes unevenly and you get bigger bubbles. You change the porcelain top less frequently with the fluval than aquatech