Businesses often claim their product can do what no other similar products on the market can.
Somehow I'm just not digging it. But I do use Matrix due to price.
I do believe Matrix has more bioavailable surface area, the logic is just that, logical. Most of the surface area of Fluval and Eheim's biomedias are in very small channels in the rock, grow some biofilm and it is gone. Many people report that the Matrix allows for lower nitrate (denitrification), something I have not heard claimed by anyone using Eheim or Fluval's biomedias. I do think they work too, but if we are discussing what works best then it can't be 'everything is okay and good enough'.