You have to look at the physical process of these products to understand their properties.
Soilmaster is clay fired at 1000 to 1500 F at this temperature clay start to vitrify and will be inert and not leach nutrient (or in very small quantity, depend of temperature). Itís almost inert like quartz sand
I beleive that Aquasoil is a specialy prepare clay mix with nutrient in the form of oxyde to ressemble what we use for trace elements and fired at lower temperature where constituant water is gone. At that point the clay lost any plasticity forever and will not be easily dissolve by water.
By playing with the amount of iron an manganese you can control the color from red to dark brown or black.
Here in presence of water and acidic environment you have lot more leaching of the constituant elements, making Aquasoil a rich complete substrat compare to inert Soilmaster.
Laterite is a kind of natural clay that lost is plasticity and constituant water by natural geologic transformation.
The good point with Soilmaster itís is CEC
Cation exchange capacity:
What CEC actually measures is the soil's ability to hold cations by electrical attraction. Cations are positively charged elements, the positive charge indicated by a + sign after the element symbol. The number of + signs indicates the amount of charge the element possesses.The five most abundant exchangeable cations in the soil are calcium (Ca++ ), magnesium (Mg++), potassium (K+), sodium (Na+) and aluminium (Al+++).
Cations are held by negatively charged particles of clay and humus called colloids. Colloids consist of thin, flat plates, and for their size have a comparatively large surface area. For this reason they are capable of holding enormous quantities of cations. They act as a storehouse of nutrients for plant roots.
For example Laterite have a CEC of only 2.7 and I beleive that Aquasoil is maybe around 5.(Itís an educated guess) but the slow leaching of nutrients feed the roots with some quantity of nutrients.
Soilmaster have a CEC of 29 to 41, meaning that any nutrient in dissolution in the water will be store in the substrat and readily available by the plants.