I am interested.
What are the tests?
Pot scrubbies have much less surface than matrix or other similar products. Even though water can move through them. Matrix also allows water to move through the material.
From Seachem link below
"Matrix™ is a high porosity biomedia that provides efficient biofiltration for the removal of nitrogenous waste. Matrix™ is a porous inorganic solid about 10 mm in diameter. Each liter of Matrix™ provides as much surface (>~700 m2) as 170 liters of plastic balls! Plastic bio-materials provide only external surface area, whereas Matrix™ provides both external and internal macroporous surface area. These macropores are ideally sized for the support of nitrifying and denitrifying bacteria. This allows Matrix™, unlike other forms of biomedia, to remove nitrate along with ammonia and nitrite, simultaneously and in the same filter."
There are many things which work to grow BB - Pot scrubbies are one, new (never used) floor waxing pads would work as well. I have used pieces of bulk filter pad too.
You can use cleaning sponges (gunk up pretty quickly though), and sponges meant for aquarium filters as well.
A canister filter has just so much room and my bet is to get a large amount of BB growing room in what I would use.
There are numerous options for many budgets as well.
The Marine Pure looks to have more BB surface area in similar amounts of product.
It is nice that there are many options to choose from and due to maintenance, bioload, and feeding, also kinds of plants (shedding and or dying off) and if you use any prefiltering options makes frequency of cleaning the Canister vary greatly.
In addition, if you have very loosely packed media sometimes the water runs through the filter so fast it doesn't stay long enough to gain the full benefit of the BB nitrification process.
My 2 cents.