You sound like you have it figured out pretty much.
Good deduction.

If the tank is rather large and you want the glass disc out of there or hate cleaning them, then the venturis are still able to beat the disc. For smaller tanks, Glass disc are still pretty decent.

The mixing value for the venturis is ideal for massive tanks, as they mix and add high flows to the glass/water mix, whereas the disc do not, only the water that flows by them and where that water goes afterwards..........small tanks do not have much mixing issues, larger tanks do.


Regards,

Tom Barr