It's actually a good question: why do people only use amazonia? I don't think I have spoken with anyone who has used any other aquasoil product...From what I can tell, there is no difference in the function - all have the same "technical specs" from what I can tell. From ADG's website:
Made from specially processed natural material from the earth.
Colloid particles capture dirt floating in the water, without any chemical treatment.
Gives clarity to the water and creates conditions ideal for healthy growth of aquatic plants.
Helps to lower the hardness level of the water.
Helps to bring the pH level of the water down to an ideal level for most of the aquatic plants.
Composed of granules of size and density ideal for the fast development of healthy plant root systems, rather conventional substrates such as sand.
Granules maintain their shape for a long period in water, holding air between them, which is vital for the long time maintenance of a planted aquarium.
Used with Power Sand stimulates the fast colonization of bacteria in the substrate and creates perfect conditions for plant root systems.
Most desirable pH level for most aquatic plants(ph 5.5 - 6.5) to develop their root systems.
Available in 3 types to suit your aquarium layout.
This last statement leads me to believe that, in fact, the only difference is visual. However, I could be wrong. Send Jeff an e-mail, I'm sure he'd be happy to answer any questions you have about any ADA products.